JP2003332081A - El fluorescent material laminated thin film and el element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an EL element of a long service life, capable of reliably generating a high luminance, and suitable for a full-color EL panel. <P>SOLUTION: In EL fluorescent material laminated thin films 50 formed on a substrate 2, an EL fluorescent material thin film 51 including a matrix material and a luminescent center, a buffer thin film 52B including a sulfide and having a thickness of 30-300 nm, and a barrier thin film 53B including an oxide and having a thickness of 5-150 nm, are laminated in this order from the side of the substrate 2. The atomic ratio of oxygen in the oxide included in the barrier thin film 53B to that of oxygen in the oxide of stoichiometric composition is more than 94% and less than 100%. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an EL (electroluminescence) device and an EL phosphor used for the same, and particularly to a thin film laminated structure of the EL phosphor.

[0002]

2. Description of the Related Art In recent years, thin-film EL devices have been actively researched as small or large-sized lightweight flat display panels. A monochrome thin film EL display using a phosphor thin film of manganese-doped zinc sulfide that emits yellow-orange light has already been put to practical use with a double insulating structure using thin film insulating layers 4A and 4B as shown in FIG. . In FIG. 5, a lower electrode 3A having a predetermined pattern is formed on a substrate 2 made of glass, and a dielectric thin film is formed as a lower insulating layer 4A on the lower electrode 3A. Also,
A light emitting layer 5 made of a phosphor thin film and an upper insulating layer 4B are sequentially formed on the lower insulating layer 4A, and an upper electrode 3B is formed on the upper insulating layer 4B so as to form a matrix with the lower electrode 3A. It is formed in a predetermined pattern.
The phosphor thin film is a glass substrate 2 for improving brightness.
It is common to anneal below the strain point.

Recently, a structure has been proposed in which the substrate 2 is made of ceramics and a thick dielectric layer is used as the lower insulating layer 4A. Furthermore, BaTiO ₃ having a high dielectric constant is used as the substrate.
There has also been proposed an element structure in which a thin plate is used, an electrode is formed on the back side of the substrate, and the thin plate is used as an insulating layer / substrate. In these structures, the substrate is aluminum oxide, BaT
Since the phosphor thin film can be annealed at high temperature because ceramics such as iO ₃ is used, high brightness can be achieved.
In addition, since a thick film or thin plate dielectric layer is used for the insulating layer, an element that is more resistant to dielectric breakdown and more reliable than an EL element that uses a thin film as the insulating layer is characterized. Further, the structure in which the phosphor thin film is sandwiched like the double insulation type structure is not always necessary. The insulating layer may be on one side only of the thick film or thin plate dielectric layer.

As a display for a personal computer, a TV,
In addition, colorization is indispensable to support display. Thin-film EL displays using sulfide phosphor thin films have excellent reliability and environmental resistance, but at present, the characteristics of EL phosphors that emit light in the three primary colors of red, green, and blue are not sufficient. , Is not suitable for color. The blue light emitting phosphor is SrS: Ce or SrGa ₂ S ₄ using SrS as a base material and Ce as an emission center:
Ce, ZnS: Tm, and ZnS: as a red light emitting phosphor.
Sm, CaS: Eu, and ZnS: as a green light emitting phosphor.
Tb, CaS: Ce, etc. are candidates and are being studied.

These phosphor thin films which emit light in the three primary colors of red, green and blue have insufficient emission brightness, efficiency and color purity, so that a color EL panel has not yet been put into practical use. In particular, although blue has a relatively high brightness obtained by using SrS: Ce, as blue for a full-color display, the color purity is shifted to the green side, and therefore, a better blue light emitting layer is obtained. Development is desired.

In order to solve these problems, Japanese Patent Laid-Open No. 7-
122364, JP-A-8-134440,
IEICE Technical Report EID98-113, pages 19-24, and Jpn.J.Appl.Ph
ys.Vol.38 (1999) pp.L1291-1292, SrGa ₂ S ₄ : Ce, CaGa ₂ S ₄ : Ce and Ba.
A thiogallate or thioaluminate-based blue phosphor having excellent brightness and color purity such as Al ₂ S ₄ : Eu is being developed.

[0007]

Under such circumstances,
In order to manufacture a high-luminance, high-quality full-color EL device with good reproducibility, further improvement of the phosphor thin film is necessary, but the thin film laminated structure including the phosphor thin film and the insulating film is also closely related to the emission brightness. Therefore, its optimization is considered to be essential. In particular, when a thioaluminate-based or thiogallate-based phosphor thin film that requires high-temperature annealing after formation is used, an element from the substrate or insulating layer to the phosphor thin film is used during high-temperature annealing. There are problems that diffusion is likely to occur, flatness between adjacent layers is likely to be deteriorated, peeling is likely to occur between adjacent layers, and this may adversely affect the reproducibility of the luminance characteristics and the element life.

An object of the present invention is to provide an EL element which is stable in high brightness and has a long life and which is suitable for a full-color EL panel.

[0009]

[Means for Solving the Problems] The above-mentioned object is as follows (1)
It is achieved by the present invention of (12). (1) An EL phosphor laminated thin film formed on a substrate, the phosphor thin film containing a host material and an emission center and a sulfide, and having a thickness of 30 to 300 nm from the substrate side.
Containing a buffer thin film which is, and an oxide, and having a thickness of 5 to 1
A barrier thin film with a thickness of 50 nm is laminated in this order,
An EL phosphor laminated thin film in which the atomic ratio of oxygen in the oxide contained in the barrier thin film is more than 94% and less than 100% with respect to the atomic ratio of oxygen in the oxide of stoichiometric composition. (2) The atomic ratio of oxygen in the oxide contained in the barrier thin film is 94.3 to 99.9% with respect to the atomic ratio of oxygen in the oxide having a stoichiometric composition.
L phosphor laminated thin film. (3) The EL phosphor laminated thin film according to (1) or (2) above, wherein a second buffer thin film is provided between the substrate and the phosphor thin film. (4) Between the substrate and the second buffer thin film,
The EL phosphor laminated thin film according to (3) above, which is provided with a second barrier thin film. (5) The EL phosphor laminated thin film according to any one of (1) to (4) above, wherein the sulfide contained in the buffer thin film is zinc sulfide. (6) The EL phosphor laminated thin film according to any one of (1) to (5) above, wherein the oxide contained in the barrier thin film is aluminum oxide. (7) The base material contains, as a main component, oxysulfide in which at least one compound selected from alkaline earth thioaluminate, alkaline earth thiogallate and alkaline earth thioindate is substituted with oxygen for part of sulfur. The EL phosphor laminated thin film according to any one of (1) to (6) above, wherein the emission center is a rare earth element. (8) In the above (1), the host material and the luminescent center contained in the phosphor thin film have a composition represented by the following composition formula.
The EL phosphor laminated thin film according to any one of to (7). Formula _{A x B y O z S w} : in M [the composition formula, A is, Mg, Ca, Sr, Ba
And at least one element selected from rare earth elements,
B is at least 1 selected from Al, Ga and In
X, y, z, and w represent atomic ratios, x = 1-5, y = 1-15, z = 0-30 (excluding 0), w = 0-30 (0 And M represents an element serving as an emission center. (9) In the composition formula, the relation between z and w is z / (z + w) = 0.01 to 0.85 (8). EL phosphor laminated thin film. (10) The EL phosphor laminated thin film according to the above (8) or (9), wherein in the composition formula, the relation between x and y is y / x = 2.1 to 3.0. (11) The above (1) to (1) wherein the emission center is Eu.
0) An EL phosphor laminated thin film according to any one of 0). (12) The EL according to any one of (1) to (11) above.
An EL device having a phosphor laminated thin film.

[0010]

The EL device of the present invention includes a phosphor thin film, a buffer thin film adjacent to the phosphor thin film, containing a sulfide such as zinc sulfide, and adjacent to the buffer thin film containing an oxide such as aluminum oxide. Including a barrier thin film
It has a phosphor laminated thin film. With such a laminated structure, the EL element of the present invention can achieve a significantly higher brightness than the conventional one.

Further, in the present invention, by optimizing the oxygen content of the oxide contained in the barrier thin film, the barrier thin film can be kept stable even during high temperature annealing. As a result, during high temperature annealing, the interaction between the barrier thin film and the phosphor thin film, between the barrier thin film and the buffer thin film, and between the barrier thin film and the lower insulating layer is suppressed, so that high brightness is achieved in the present invention. Moreover, an EL element having a long life can be obtained with good reproducibility.

By applying the present invention, blue primary colors, green primary colors, and red primary colors are emitted with a higher brightness than ever before, and
Since an EL element having a long emission life can be stably obtained, a full color panel for a display can be realized by using these.

The process by which the present inventors have reached the present invention will be described below.

The present inventors firstly describe a phosphor thin film made of BaAl ₂ S ₄ : Eu, which is excellent as a blue EL material,
Ten EL elements having an EL phosphor laminated thin film composed of a buffer thin film made of zinc sulfide and a barrier thin film made of aluminum oxide were manufactured under the same manufacturing conditions. For EL phosphor laminated thin film, 700 ° C in air
Was annealed. When the luminance characteristics of these elements were evaluated, variations in the luminance-voltage (LV) characteristics were recognized, and when compared at the same voltage, the luminance was several times different. The cause is that when forming each thin film in a vacuum chamber, there are minute variations in the film forming conditions, and there are also minute variations in the amount of gas such as H ₂ O and O ₂ remaining in the vacuum chamber. It was speculated that this affected the reproducibility of the emission characteristics of the EL phosphor laminated thin film.

Therefore, by strictly controlling the film forming conditions after strictly controlling the residual gas in the vacuum chamber, the composition of each thin film was intentionally changed and the brightness characteristics were investigated. It has been found that the composition, especially its oxygen content, is closely related to the brightness characteristics. Specifically, by reducing the oxygen content of the oxide contained in the barrier thin film by a predetermined amount less than the oxygen content of the oxide having a stoichiometric composition,
We have found that high brightness can be obtained. If the conditions for forming the barrier thin film are controlled so that the oxygen content falls within this range, high brightness and light emission can be obtained even when using a thioaluminate-based or thiogallate-based phosphor material that requires high-temperature annealing. It was found that an EL phosphor laminated thin film having a long life can be obtained with good reproducibility.

Generally, not only oxides but also many compounds are
Stability is considered to be high when the composition is stoichiometric. However, this is true for a bulk material in which a crystal structure such as a single crystal or a polycrystal is incorporated, and particularly when the material is amorphous or a thin film even if a crystal phase exists, It is considered that the stoichiometric composition is not always stable in the case of a structure in which another thin film is laminated like an EL device.

In the present invention, it is not clear why the oxide contained in the barrier thin film is in an oxygen-deficient state to realize high brightness and long life, but in the following experiment simulating the EL device formation process, The following phenomena were observed.

In this experiment, first, a barrier thin film made of aluminum oxide whose oxygen content was controlled by controlling the forming conditions was independently formed on the substrate. In these barrier thin films, the atomic ratio O / Al, which represents the oxygen content,
Was set within the range of approximately 1.4 to 1.7. In addition,
The barrier thin film is aluminum oxide (Al ₂
When it is composed of O ₃ ), the atomic ratio O / Al is 1.
It is 5. Therefore, the atomic ratio O / in the barrier thin film
Al is O / Al in the stoichiometric composition of Al ₂ O ₃ .
Of 93.33 to 113.33%. Then, like the actual EL element, annealing was performed at 700 ° C. in air.

When the composition of the barrier thin film was measured by X-ray fluorescence analysis before and after annealing, the composition stability of the barrier thin film was different depending on the oxygen content of the barrier thin film. Specifically, the atomic ratio O / A after annealing
When l was outside the range defined by the present invention, the change in atomic ratio O / Al due to annealing was large. In contrast, if the atomic ratio O / Al after annealing was within the range defined by the present invention, the atomic ratio O / A before and after annealing was
Almost no change was observed in l.

From these results, it can be inferred that the oxygen content of the barrier thin film in an actual EL device has an effect that the barrier thin film having an oxygen content higher than the range limited by the present invention,
For example, a barrier thin film with the same oxygen content as the stoichiometry will release oxygen to become more stable as a result of becoming unstable when activated by high temperature annealing. At that time, it is considered that the buffer thin film and the phosphor thin film in the vicinity are oxidized and the luminance characteristics and the light emission life are deteriorated. On the other hand, since the barrier thin film having less oxygen content than the range limited by the present invention has low stability, when activated by high temperature annealing, it tries to take in various elements such as oxygen from a thin film in the vicinity, and as a result, It is thought that this affects the composition of the thin film and deteriorates the luminance characteristics and the emission lifetime. Further, it is considered that if elements enter and leave the barrier thin film during annealing, the barrier thin film reacts with the buffer thin film, and the flatness of the interface between the two thin films is impaired.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below.

There are still many unclear points about the emission mechanism of the thioaluminate, thiogallate or thioindate EL thin film.

The blue emission BaAl ₂ S ₄ : Eu thin film is analyzed in the materials p16 to p21 of the 22nd research group of the EL Subcommittee of the 125th Committee on Photoelectric Interconversion, Japan Society for the Promotion of Science. Here, BaAl ₂ S ₄ has different regions emitting light in the film thickness direction, strongly emits light near the film surface, has a composition distribution in the film thickness direction, and contains a large amount of oxygen. However, the mechanism of strong light emission has not been clarified.

Ternary compounds such as alkaline earth thioaluminates, alkaline earth thiogallates and alkaline earth thioindates usually have a higher crystallization temperature than binary compounds such as ZnS and SrS, so that film formation is possible. Formation by a high temperature process that raises the temperature to 500 ° C. or higher and an annealing oxygenation process that performs high temperature annealing at 700 ° C. or higher in an oxidizing atmosphere are necessary. In such a process, it is considered that the BaAl ₂ S ₄ : Eu thin film has the EL matrix material, the emission center, and the thin film structure optimized under appropriate conditions, and strong light emission can be obtained.

The annealing oxygenation process in which annealing is performed in an oxidizing atmosphere has the effect of dramatically increasing the EL emission brightness of the phosphor thin film. When the thin film containing the ternary compound as a base material contains oxygen, crystallization is promoted during the post-treatment such as film formation of this base material or annealing after the film formation, and the luminescence center added to the thin film It is considered that the (rare earth element) has an effective transition in the compound crystal field, and high-luminance light emission can be obtained.

The light emitting element has a life in which the luminance deteriorates with the passage of the light emitting time. The composition in which oxygen and sulfur are mixed improves the life characteristics and prevents the deterioration of brightness. Compared to the case where the base material is pure sulfide, it becomes stable in air due to the mixture of the compound with oxygen. It is considered that this is because the stable oxide component protects the sulfide component in the film from the air. Therefore, according to the studies by the inventors, the ratio of sulfide to oxide has an optimum value described later.

The contents of sulfur and oxygen in the base material may be adjusted by the composition of the raw materials, but as described above, the annealing treatment is performed especially in the oxidizing atmosphere after forming the thin film, and the conditions of this annealing treatment are set. It is preferable to adjust by controlling. The present invention provides an EL phosphor laminated thin film having a structure in which a phosphor thin film, a sulfide-containing buffer thin film, and an oxide-containing barrier thin film are laminated, and the laminated thin film is annealed in an oxidizing atmosphere. By applying the above, it is possible to easily control the amounts of sulfur and oxygen in the phosphor thin film during annealing. As a result, by using the EL phosphor laminated thin film of the present invention, it is possible to realize an EL element that can obtain unprecedented high brightness with good reproducibility and has little brightness deterioration.

The barrier thin film functions as a cap layer for controlling the amount of oxygen introduced into the phosphor thin film from the atmosphere during annealing in the oxidizing atmosphere. Specifically, the phosphor thin film is appropriately oxidized during annealing to prevent excessive oxidation. The barrier thin film also prevents sulfur from flowing out of the phosphor thin film during annealing. On the other hand, the buffer thin film functions as a sulfur control layer that optimizes the amount of sulfur in the phosphor thin film during annealing. The buffer thin film also has the effects described below.

In addition to these functions, the barrier thin film has 5
In the case of a relatively thin thickness of about 0 nm, when it is provided in combination with the buffer thin film, it also functions as an electron injection layer to the phosphor thin film for mainly emitting light with high brightness. The buffer thin film functions as an electron injection enhancing layer that further accelerates the injected electrons and injects them into the phosphor thin film.

A constitutional example of the EL phosphor laminated thin film of the present invention,
As shown in FIG. In FIG. 3, in the structure in which the EL phosphor laminated thin film 50 is provided on the lower insulating layer 4A, the phosphor thin film 51, the buffer thin film 52, and the barrier thin film 5 from the lower insulating layer 4A side.
It is laminated in the order of 3. That is, in the present invention, the respective thin films are laminated so that the surface of the EL phosphor laminated thin film 50 on the side opposite to the substrate 2 is constituted by the barrier thin film 53, and annealing is performed in an oxidizing atmosphere in this state. Good.

However, in order to facilitate the control of the oxygen content and the sulfur content of the phosphor thin film 51, in the structure shown in FIG. It is preferable that the body thin film is sandwiched between the buffer thin films. This structure is shown in FIG. E in FIG.
The L phosphor laminated thin film 50 includes a lower buffer thin film 52A, a phosphor thin film 51, an upper buffer thin film 52B, and a barrier thin film 5.
It has a structure of stacking in the order of 3. More preferably, a second barrier thin film is provided on the substrate side of the second buffer thin film. That is, as shown in FIG.
If the phosphor laminated thin film 50 has a structure in which the lower barrier thin film 53A, the lower buffer thin film 52A, the phosphor thin film 51, the upper buffer thin film 52B, and the upper barrier thin film 53B are laminated in this order, that is, the phosphor thin film is sandwiched between them. If buffer thin films are provided on both sides and barrier thin films are further provided on both sides,
Higher brightness can be obtained. The phosphor thin film and the buffer thin film are preferably provided in contact with each other, and the buffer thin film and the barrier thin film are preferably provided in contact with each other.

In order to exert the functions of the barrier thin film and the buffer thin film, it is necessary to control the film thickness of these thin films.

The thickness of the barrier thin film is 5 to 150 nm, preferably 10 to 100 nm, and specifically, it may be appropriately determined within this range depending on the film forming conditions and annealing conditions.
If the barrier thin film is too thin, the phosphor thin film is excessively oxidized during annealing in an oxidizing atmosphere, and the amount of sulfur flowing out from the phosphor thin film increases, so that high brightness cannot be obtained. On the other hand, if the barrier thin film is too thick, the phosphor thin film is not sufficiently oxidized, so that high luminance cannot be obtained and luminance deterioration is likely to occur.

The buffer thin film has a thickness of 30 to 300 nm,
The thickness is preferably 50 nm to 200 nm, and specifically, it may be appropriately determined within this range according to the film forming conditions and the annealing conditions. If the buffer thin film is too thin, the amount of sulfur in the phosphor thin film tends to become insufficient, and if the buffer thin film is too thick, the amount of oxygen in the phosphor thin film tends to become insufficient. Further, if the buffer thin film is too thin, the function as the electron injection enhancing layer described above becomes poor. Specifically, the light emission start voltage (threshold voltage) increases, and the voltage for driving the EL element to emit light increases. Further, since the buffer thin film is an insulator, if the buffer thin film is thick, the capacitance of the EL phosphor laminated thin film is effectively increased, so that the light emission start voltage (threshold voltage) is increased.

In the present invention, the most preferable thickness range of the barrier thin film and the buffer thin film is the lower barrier thin film (0
˜50 nm) / lower buffer thin film (50 to 200 nm) / phosphor thin film / upper buffer thin film (50 to 200 nm) / upper barrier thin film (30 to 70 nm).

The barrier thin film is a thin film containing an oxide.
And is composed essentially of oxides, except for trace amounts of impurity elements
Preferably. This oxide is a metal element and
And / or may contain only one metalloid element
Or two or more types may be included. Used for barrier thin film
Examples of usable oxides include yttrium oxide.
(Y₂O₃) And other rare earth oxides, silicon oxide (Si
O₂), Tantalum oxide (Ta₂O _Five), Strontium titanate
Tium (SrTiO₃), Barium titanate (BaTi
O ₃), Lead titanate (PbTiO₃), Lead niobate (Pb
NbO₃), Lead zirconate titanate (PZT), Pb
(Mg_1/3Nb_2/3) O₃And PbTiO₃Or a mixture with
Complex oxide (PMN-PT), zirconium oxide (ZrO
₂), Hafnium oxide (HfO₂),Aluminum oxide
(Al₂O₃) Is mentioned. Of these, oxide-it
Rium (Y₂O₃) Rare earth oxides such as aluminum oxide
Mu (Al₂O₃), Zirconium oxide (ZrO₂), Oxidation
Hafnium (HfO₂) Has good injection characteristics into the phosphor thin film.
Therefore, aluminum oxide (Al₂O₃)
Is preferred. In addition, in this description, the oxide is chemically
In the barrier thin film, it is shown as a stoichiometric compound.
There is a certain amount of oxygen deficiency in the oxide actually contained in
Exists

The barrier thin film may have a multi-layer structure in which two or more thin films having different compositions are laminated. In any case, when the EL phosphor laminated thin film is annealed in an oxidizing atmosphere, the barrier thin film having the predetermined thickness may be present in the uppermost layer of the EL phosphor laminated thin film.

In the present invention, the oxide contained in the barrier thin film is in a state in which oxygen is deficient as compared with the stoichiometric composition. If the atomic ratio of oxygen in the barrier thin film is equal to or higher than the atomic ratio of oxygen in the stoichiometric composition, the characteristics of the EL phosphor laminated thin film will deteriorate due to high temperature annealing in an oxidizing atmosphere. However, even if the atomic ratio of oxygen in the barrier thin film is too small, the characteristics of the EL phosphor laminated thin film deteriorate due to high temperature annealing in an oxidizing atmosphere. Therefore, in the present invention, the atomic ratio of oxygen in the oxide contained in the barrier thin film is more than 94% and less than 100% with respect to the atomic ratio of oxygen in the oxide of the stoichiometric composition, preferably 94.3 to 99. 9%. The oxygen content (atomic ratio of oxygen) limited in the present invention needs to be satisfied in all barrier thin films included in the EL phosphor laminated thin film.

In the present specification, the atomic ratio of oxygen in an oxide is O / Me when the metal element and the metalloid element contained in the oxide are both represented by Me and oxygen is represented by O.
It is represented by. For example, if the oxide is aluminum oxide, the stoichiometric compound is Al ₂ O ₃ ,
The atomic ratio O / Al is 1.5. On the other hand, the oxide having an oxygen-deficient composition that constitutes the barrier thin film is Al ₂ O _2.88.
, The atomic ratio O / Al is 1.44. At this time, the ratio of the atomic ratio of oxygen in the barrier thin film to the atomic ratio of oxygen in the stoichiometric composition is 100 × 1.44 / 1.5 = 96 (%). When the oxide is a double oxide containing two or more kinds of metal elements and / or metalloid elements, the atomic ratio O /
Calculate Me.

The atomic ratio of oxygen in the barrier thin film can be confirmed by electron probe microanalysis (EPMA), fluorescent X-ray analysis (XRF), X-ray photoelectron analysis (XPS), Rutherford backscattering method (RBS) and the like. it can.

The buffer thin film is a thin film containing sulfide,
A thin film made of sulfide is particularly preferable. Examples of the sulfide include rare earth sulfides such as yttrium sulfide (Y ₂ S ₃ ), zinc sulfide (ZnS), magnesium sulfide (MgS), strontium sulfide (SrS), calcium sulfide (CaS), barium sulfide (BaS). Is mentioned. Of these, ZnS is preferable as the injection acceleration layer for the phosphor thin film.

The buffer thin film may contain only one kind of these compounds, or may contain two kinds or more. Further, the buffer thin film may have a multi-layered structure in which two or more thin films having different compositions are laminated.

The barrier thin film and the buffer thin film are formed by sputtering, vapor deposition by electron beam heating, vapor deposition by resistance heating, CVD, ion plating,
Although various existing methods such as a laser ablation method and a sol-gel coating method can be used,
It is particularly preferable to use the vapor deposition method.

When forming the barrier thin film, the forming conditions may be controlled so that an oxide thin film satisfying the oxygen deficiency amount limited in the present invention can be formed. Hereinafter, a typical method will be described with respect to conditions for forming a controlled object.

The sputtering method is a method of forming a thin film by sputtering a sputtering target as a raw material in a sputtering chamber in a sputtering gas such as Ar gas. When using a sputter target made of oxide, a thin film with the same composition as the target is obtained at the beginning of use of the target, but oxygen is released from the target surface as the usage time increases, so the resulting thin film also becomes oxygen deficient. . Therefore, in order to stably obtain an oxide thin film having a stoichiometric composition with good reproducibility, not only Ar gas but also 1 to 5 oxygen gas is added to Ar gas as a sputtering gas to be flown during film formation.
It is generally practiced to use a mixed gas added at about volume%. In the present invention, since the barrier thin film made of the oxygen-deficient oxide is formed, the residual gas in the vacuum chamber is eliminated as much as possible, preferably, the pressure in the vacuum chamber is set to 1 × 10 ⁻⁴ Pa or less, and then the Ar gas is reduced to 0. Sputtering is preferably carried out while flowing a mixed gas to which 0.055 to 0.5% by volume of oxygen gas is added as a sputtering gas. Thereby, the oxygen deficiency state limited by the present invention can be easily realized.

The electron beam heating vapor deposition method is a method of forming a thin film on a substrate by heating by accelerating electrons to an evaporation source in a metal crucible or the like in a vacuum chamber to heat and evaporate the electrons.

The degree of vacuum in the vacuum chamber when forming a thin film is about 0.3 to 5 Pa in the sputtering method, whereas it is 5 × 10 ⁻⁵ to 1 × 10 ⁻² Pa in the vapor deposition method by electron beam heating. However, the two are very different. Therefore, in the vapor deposition method,
Various factors are entangled between the evaporation source is evaporated and the film is attached to the substrate to form a thin film, which affects the characteristics of the obtained thin film. Various factors include, for example, the substrate temperature, the vapor deposition rate, the residual gas in the vacuum chamber, the acceleration power of the electron beam, and the type and flow rate of the atmospheric gas when controlling the film forming atmosphere. In order to control the oxygen deficiency when forming the barrier thin film in the present invention, these factors may be controlled. Specifically, when an oxide having a stoichiometric composition is used as the evaporation source, the higher the substrate temperature,
The higher the deposition rate, the smaller the residual gas (particularly H ₂ O component), the smaller the flow rate of the atmospheric gas (oxygen gas in the oxide), and the higher the power of the electron beam, the more the oxide thin film with a large amount of oxygen vacancies is obtained. To be On the other hand, if these factors are changed in the opposite direction, an oxide thin film with little oxygen deficiency or excess oxygen can be obtained. In the vapor deposition method using electron beam heating, an oxide thin film having a target composition can be obtained with good reproducibility only after the above factors are sufficiently controlled and controlled.

In forming the EL device having the structure shown in FIG. 1, after forming the lower barrier thin film 53A and the lower buffer thin film 52A and before forming the phosphor thin film 51,
It may be annealed. By performing this annealing, the lower barrier thin film 53A made of oxide can be kept in a more stable state. The annealing conditions may be the same as the annealing conditions for the phosphor thin film described later. However, this annealing may be performed in an oxidizing atmosphere or in vacuum.

The buffer thin film and the barrier thin film in the present invention have completely different functions from the insulating layer in the double insulation type structure shown in FIG. Further, an EL phosphor laminated thin film having a barrier thin film and a buffer thin film each having a thickness limited by the present invention has not been known hitherto.

The above-mentioned Japan Society for the Promotion of Science Optoelectronic Mutual Conversion No. 1
25th Committee EL Subcommittee 22nd Study Group Materials p16-p2
1 has a Ta ₂ O ₅ insulating layer (270n) on a glass substrate.
m), ZnS buffer layer (90 to 360 nm), BaAl ₂
A sample having a structure in which an S ₄ : Eu ²⁺ light emitting layer (400 nm) and a ZnS cap layer (40 nm) are laminated is described. In this sample, the Ta ₂ O ₅ insulating layer is similar to the barrier thin film of the present invention, and the ZnS buffer layer and ZnS
The cap layer is similar to the buffer thin film in the present invention.
However, in this sample, there is no thin film corresponding to the barrier thin film on the ZnS cap layer. Moreover, the heat treatment for this sample is for preventing the release of sulfur from the BaAl ₂ S ₄ : Eu ²⁺ light emitting layer, and is 800 to 1000 ° C. in an Ar atmosphere after the ZnS cap layer is formed.
Has been held for 2 minutes. On the other hand, in the present invention, it is necessary to utilize both the barrier thin film and the buffer thin film in order to control the oxygen amount and the sulfur amount in the phosphor thin film during the heat treatment in the oxidizing atmosphere. Therefore, unlike the EL device of the present invention, the sample does not achieve the effects of the present invention.

Further, Japanese Patent Laid-Open No. 1-206594 discloses a transparent electrode on a glass substrate having a first thickness of 0.5 μm.
Dielectric layer (Ta ₂ O ₅ ), ZnS buffer layer, CaS:
Eu light emitting layer, 0.5 μm thick second dielectric layer (Ta ₂ O
₅ ) and a back electrode are laminated to form a thin film EL device. In this thin film EL device, the composition of the light emitting layer is different from the composition defined in the present invention, and the thickness of the second dielectric layer is thicker than the thickness of the barrier thin film in the present invention.
There is no ZnS buffer layer on the upper side of the light emitting layer, and no annealing is performed in an oxidizing atmosphere. Therefore, this thin film EL device is different from the EL device of the present invention.
The effect of the present invention is not realized.

In the present invention, the phosphor thin film contains a base material and an emission center. Host material and the light emitting center, formula _{A x B y O z S w} : is preferably one represented by M. In the composition formula, A is at least one element selected from Mg, Ca, Sr, Ba and rare earth elements, and B is A
At least one element selected from l, Ga, and In, and M represents an element serving as an emission center. Also, x,
y, z and w represent atomic ratios, x = 1-5, y = 1-15, z = 0-30 (excluding 0), w = 0-30 (excluding 0), and preferably x = 1 to 5, y = 1 to 15, z = 3 to 30, and w = 3 to 30.

The base material represented by the above composition formula is an alkaline earth thioaluminate, an alkaline earth thiogallate,
It is an oxysulfide in which a part of sulfur is replaced with oxygen in a sulfide composed of alkaline earth thioindate, rare earth thioaluminate, rare earth thiogallate, rare earth thioindate, or a mixture containing two or more of these. In addition, in this specification, an alkaline earth element is Mg, Ca, Sr, and Ba.

The sulfide is preferably at least one of alkaline earth thioaluminate, alkaline earth thiogallate and alkaline earth thioindate, and particularly preferably at least one of barium thioaluminate and strontium thiogallate. Since these have high crystallization temperatures, they are preferable for application of the present invention. Particularly, barium thioaluminate to which Eu is added as an emission center and strontium thiogallate to which Eu is added as an emission center are most preferable. Preferably, these combinations are effective for emitting blue and green with high color purity with high brightness. Further, in these preferable sulfides, those in which a part of the alkaline earth element is replaced with a rare earth element are also preferable.

Hereinafter, the case where an alkaline earth element is mainly used as the element A will be described in detail.

The phosphor thin film is preferably crystallized, but may be in an amorphous state having no clear crystal structure.

Crystals contained in the phosphor thin film are A ₅
B ₂ S ₈ , A ₄ B ₂ S ₇ , A ₂ B ₂ S ₅ , AB ₂ S ₄ , AB ₄
One or more of S ₇ , A ₄ B ₁₄ S ₂₅ , AB ₈ S ₁₃ , and AB ₁₂ S ₁₉ are preferable, and AB ₂ S ₄ crystal is particularly preferable. In the phosphor thin film, O may replace a part of S in the crystal.

When A _x B _y O _{z Sw} is a stoichiometric compound, this compound has x {A (O, S)} and (y
/ 2) {B ₂ (O, S) ₃ }. Therefore, the stoichiometric composition is almost obtained when z + w = x + 3y / 2. The composition of the phosphor thin film is preferably near the stoichiometric composition in order to obtain high-luminance light emission, and specifically, 0.9 ≦ (x + 3y / 2) / (z + w) ≦ 1.1. Is preferred.

The element M added as a luminescence center is preferably a rare earth element. The rare earth element is at least Sc, Y, La, Ce, Pr, Nd, Gd, Tb, H.
It is selected from o, Er, Tm, Lu, Sm, Eu, Dy and Yb. The emission centers to be combined with the barium thioaluminate host material are Eu for making a blue phosphor, Ce, Tb, Ho for making a green phosphor, and Sm, Yb, Nd for making a red phosphor. Of these, Eu is most preferably used as the blue phosphor. Further, the strontium thiogallate matrix material and Eu
When combined with, a green phosphor is obtained, and when a strontium thioindate host material or a barium thioindate host material is combined with Eu, a red phosphor is obtained.
The addition amount of the element serving as the emission center is preferably 0.5 to 10 atom% with respect to the element A in the composition formula.

As described above, the composition in which oxygen and sulfur are mixed improves brightness characteristics and life characteristics and prevents deterioration of brightness. Compared to the case where the base material is pure sulfide, it becomes stable in air due to the mixture of the compound with oxygen. Further, the composition of the base material is preferably such that the element B is in excess with respect to the stoichiometric composition. For example, when the base material has a composition of BaAl ₂ S ₄ , that is, near BaS—Al ₂ S _3, it is preferable that Al / Ba> 2. Excessive Al ₂ S ₃ is unstable to water, but by introducing oxygen into this excess Al, it becomes a stable oxide component rather than an unstable sulfide component. Then, this oxide component protects the light emitting portion from the air. In order to achieve high brightness and long life, the oxygen content in the base material is adjusted so that z / (z + w) = 0.01 to 0.85 in the above composition formula, and the above composition formula is also used. It is desirable that y / x = 2.1 to 3.0, and more preferably y / x = 2.3 to 2.9. In order to obtain a particularly high brightness and a long life, it is desirable that z / (z + w) = 0.1 to 0.3 and y / x = 2.6 to 2.8.

The composition of the phosphor thin film was determined by X-ray fluorescence analysis (XR
F), X-ray photoelectron analysis (XPS), TEM-EDS (Tr
ansmission Electron Microscopy-Energy Dispersive
It can be confirmed by X-ray Spectroscopy).

The film thickness of the phosphor thin film is not particularly limited, but if it is too thick, the driving voltage increases, and if it is too thin, the luminous efficiency decreases. Specifically, depending on the fluorescent material, it is preferably 100 to 2000 nm, more preferably 1 nm.
It is about 50 to 700 nm.

To obtain the phosphor thin film, for example, the following reactive vapor deposition method is preferable. Here, a barium thioaluminate: Eu phosphor thin film will be described as an example.

In order to form a barium thioaluminate: Eu phosphor thin film, a barium thioaluminate pellet containing Eu was prepared, and this pellet was used as an evaporation source in the vacuum chamber in which H ₂ S gas was introduced. Electron beam) vapor deposition may be used. Here, H ₂ S gas is used to make up for the lack of sulfur.

In addition, a method using a multi-source reactive vapor deposition method can also be used. In that case, for example, a binary reactive vapor deposition method using Eu-added barium sulfide pellets, aluminum sulfide pellets and H ₂ S gas is preferable.

Eu, which is the emission center, is added to the evaporation source in the form of metal, fluoride, oxide or sulfide. Eu of evaporation source
Content and Eu in the thin film formed by using the evaporation source
Since it is different from the content, the Eu content in the evaporation source is adjusted so that the desired content is obtained in the thin film.

The substrate temperature during vapor deposition is preferably room temperature to 7
The temperature is 00 ° C, and more preferably 400 to 550 ° C. If the substrate temperature is too low, not only the interaction between the phosphor thin film and the buffer thin film and barrier thin film located therebelow cannot be well drawn out, but also the crystallinity of the phosphor thin film deteriorates. On the other hand, if the substrate temperature is too high, the interface between the phosphor thin film and the buffer thin film located thereunder deteriorates, the unevenness of the phosphor thin film surface becomes severe, and pinholes are generated in the thin film to cause EL element. The problem of current leakage easily occurs. In addition, the thin film may turn brown.

After film formation, annealing treatment is performed in an oxidizing atmosphere. By this annealing, the host material of the phosphor thin film can be oxysulfide whose oxygen content is appropriately controlled, and the crystallinity of the phosphor thin film can be remarkably improved. The annealing temperature is preferably 500 to 1000 ° C, especially 650 to 800 ° C. The annealing is preferably performed in air or an atmosphere having a higher oxygen concentration than air. The annealing time is usually 1 to 60 minutes, preferably 5 to 30 minutes. If the annealing time is too short, the effect of annealing cannot be fully realized. On the other hand, even if the annealing time is remarkably lengthened, the effect of annealing does not remarkably increase, and constituent elements other than the phosphor thin film (electrodes, substrates, etc.) may be damaged by heating for a long time. Absent.

The formed phosphor thin film is preferably a highly crystalline thin film. The crystallinity can be evaluated by, for example, X-ray diffraction. To increase crystallinity,
Make the substrate temperature as high as possible. Further, the above-mentioned annealing is also effective.

The pressure during vapor deposition of the phosphor thin film is preferably 1.33 × 10 ^{-4 to} 1.33 × 10 ^-1 Pa. In particular,
The pressure was adjusted to 6.65 × 10 ⁻³ to 6.65 × 10 ⁻² by adjusting the introduction amount of H ₂ S gas for compensating for sulfur.
Pa is good. If the pressure is higher than this, the operation of the E gun becomes unstable, and composition control becomes extremely difficult. The amount of H ₂ S gas introduced is preferably 5 to 200 SCCM, particularly 10 to 30 SCCM, although it depends on the capacity of the vacuum system.

If necessary, the substrate may be moved or rotated during vapor deposition. By moving and rotating the substrate, the film composition becomes uniform and variations in the film thickness distribution are reduced.

When the substrate is rotated, the rotation speed of the substrate is preferably 10 times / min or more, more preferably 10 to 50 times / min, and especially about 10 to 30 times / min. If the rotation speed of the substrate is further increased, it becomes difficult to seal the vacuum chamber to keep it airtight. Also, if the rotation speed is too slow, compositional unevenness occurs in the film thickness direction in the tank,
The characteristics of the manufactured light emitting layer deteriorate. The rotating means for rotating the substrate can be configured by a known rotating mechanism using a power transmission mechanism, a reduction mechanism, and the like in which a power source such as a motor and a hydraulic rotating mechanism is combined with a gear, a belt, a pulley, and the like.

Any heating means for heating the evaporation source or the substrate may be used as long as it has a predetermined heat capacity and reactivity, and examples thereof include a tantalum wire heater, a sheath heater, and a carbon heater. The heating temperature by the heating means is preferably 1
The temperature control accuracy is preferably about ± 1 ° C at 1000 ° C, more preferably about ± 0.5 ° C.

In order to use the EL phosphor laminated thin film of the present invention as an EL device, the light emitting layer 5 in the double insulation type structure shown in FIG.
As an example, the EL phosphor laminated thin film 50 of the present invention as shown in FIGS. 1 to 3 is used, or the above-described structure in which an insulating layer made of a thick or thin dielectric layer is provided on only one side. The EL phosphor laminated thin film of the present invention is used for the light emitting layer. In the latter case, for example, the structure shown in FIG. 4 may be used. In FIG. 4, a lower electrode 3A, an insulating layer 4 composed of a thick film dielectric layer, a light emitting layer 5 (EL phosphor laminated thin film 50) and an upper electrode 3B are formed on a substrate 2. In the EL elements shown in FIGS. 4 and 5, respectively,
An intermediate layer such as a layer for increasing adhesion, a layer for relieving stress, a layer for controlling reaction may be provided between adjacent layers such as an insulating layer, a light emitting layer, and an electrode. The thick film surface may be improved in flatness by polishing or using a flattening layer.

The material used as the substrate has a heat resistant temperature or melting point of preferably 600 ° C. or higher, more preferably 700 ° C. or higher, and further preferably 800 so that it can withstand the formation temperature of each layer of the EL device and the annealing temperature of the EL device. ℃
It is not particularly limited as long as it is the above and an EL element can be formed by a functional thin film such as a light emitting layer formed thereon and can maintain a predetermined strength.
Specifically, glass or aluminum oxide (Al ₂
O ₃ ), forsterite (2MgO · SiO ₂ ), steatite (MgO · SiO ₂ ), mullite (3Al ₂ O ₃
2SiO ₂ ), beryllium oxide (BeO), aluminum nitride (AlN), silicon nitride (Si ₃ N ₄ ), silicon carbide (SiC + BeO) and other ceramic substrates, and heat resistant glass substrates such as crystallized glass. Among these, the heat resistance temperature of the aluminum oxide substrate and the crystallized glass is particularly preferably about 1000 ° C. or higher, and when heat conductivity is required, beryllium oxide, aluminum nitride, silicon carbide and the like are preferable. In addition to this, a quartz, thermally oxidized silicon wafer, or other metal substrate such as titanium, stainless steel, Inconel, or an iron-based material can also be used. When a conductive substrate made of metal or the like is used, a structure in which a thick film having electrodes inside is formed on the substrate is preferable.

As the material of the dielectric thick film (lower insulating layer), a known dielectric thick film material can be used. This material preferably has a relatively large dielectric constant, and for example, a lead titanate-based material, a lead niobate-based material, a barium titanate-based material, or the like is preferred. The dielectric thick film has a resistivity of 10
^{It is 8} Ω · cm or more, especially about 10 ¹⁰ to 10 ¹⁸ Ω · cm.
A substance having a relatively high relative permittivity is preferable, and the relative permittivity ε is preferably ε = 100.
It is about 10,000. The film thickness is 5 to 50 μm
Is preferable, and 10 to 30 μm is particularly preferable. The method for forming the thick dielectric film is not particularly limited as long as a film having a predetermined thickness can be relatively easily obtained, but a sol-gel method, a printing firing method, or the like is preferable. When the printing and firing method is used, the particle size of the material is appropriately adjusted, and the material is mixed with a binder to obtain a paste having an appropriate viscosity. This paste is formed on a substrate by a screen printing method and dried to form a green sheet. The green sheet is fired at an appropriate temperature to obtain a thick film.

The constituent material of the thin film insulating layer (upper insulating layer) is, for example, silicon oxide (SiO ₂ ), silicon nitride (S
i ₃ N ₄ ), tantalum oxide (Ta ₂ O ₅ ), strontium titanate (SrTiO ₃ ), yttrium oxide (Y
₂ O ₃ ), barium titanate (BaTiO ₃ ), lead titanate (PbTiO ₃ ), lead zirconate titanate (PZ
T), zirconia (ZrO ₂ ), silicon oxynitride (SiON), aluminum oxide (Al ₂ O ₃ ),
Lead niobate and PMN-PT are preferred. The thin film dielectric layer may have a structure of a single layer or a multilayer of layers containing at least one of these. As a method for forming an insulating layer with these materials, vapor deposition, sputtering, CVD
An existing method such as a method may be used. In this case, the thickness of the insulating layer is preferably 50 to 1000 nm, particularly 10
It is about 0 to 500 nm. As described above, the upper insulating layer may not be provided.

The lower electrode is formed between the substrate and the lower insulating layer or in the lower insulating layer. The lower electrode is exposed to a high temperature when the light emitting layer is annealed, and is also exposed to a high temperature when the lower insulating layer is formed when the lower insulating layer is formed of a thick film. Therefore, the lower electrode preferably has excellent heat resistance, and more specifically, it is preferably a metal electrode.
The metal electrode is a commonly used metal electrode containing one or more of palladium, rhodium, iridium, rhenium, ruthenium, platinum, silver, tantalum, nickel, chromium, titanium, etc. as a main component. You may

On the other hand, the upper electrode is usually an electrode having a light-transmitting property in a predetermined emission wavelength range, for example, a transparent electrode made of ZnO, ITO, IZO or the like in order to take out light emission from the side opposite to the substrate. preferable. ITO usually contains In ₂ O ₃ and SnO in a stoichiometric composition.
The amount may deviate somewhat from this. The mixing ratio of SnO ₂ with respect to In ₂ O ₃ is preferably 1 to 20% by mass, more preferably 5 to 12% by mass. The mixing ratio of ZnO to In ₂ O ₃ in IZO is usually 12 to 32.
It is about mass%. When the emitted light is extracted from the substrate side using a transparent substrate, the lower electrode is a transparent electrode.

The electrodes may contain silicon as a main component. This silicon electrode is made of amorphous silicon (a) even if it is polycrystalline silicon (p-Si).
-Si) may be used, and if necessary, single crystal silicon may be used. The silicon electrode is doped with impurities to ensure conductivity. The dopant used as an impurity may be any dopant that can ensure a predetermined conductivity, and a normal dopant used in silicon semiconductors can be used. Specifically, B, P, As, S
b and Al are preferred. The concentration of the dopant is 0.0
It is preferably about 01 to 5 atom%.

The electrodes are formed by vapor deposition, sputtering, C
The method may be appropriately selected from existing methods such as the VD method, the sol-gel method, and the printing and firing method. Especially, when the structure is provided with a dielectric thick film including an electrode inside, the electrode is the same method as the dielectric thick film. Is preferably formed.

The resistivity of the electrode is such that an electric field is efficiently applied to the light emitting layer.
To give, preferably 1 × 10 ^-2Ω · cm or less, more
Preferably 5 × 10^-Five~ 1 x 10^-3Ω · cm. electrode
The film thickness of is different depending on the electrode constituent material, but is preferable
Is 50 to 2000 nm, more preferably 100 to 1000
It is about nm.

[0083]

EXAMPLES The present invention will be described in more detail below by showing specific examples of the present invention.

EL using the EL phosphor laminated thin film of the present invention
A device was produced. The EL element has the configuration of FIG. 4 which has already been described.

Both the substrate 2 and the insulating layer 4 are made of BaTi.
O ₃ -PbTiO ₃ system dielectric material (relative permittivity 2000)
And the lower electrode 3A was made of Pd. First,
A sheet to be the substrate 2 was prepared, and a paste to be the lower electrode 3A and the insulating layer 4 was screen-printed on the sheet to form a green sheet, which was simultaneously fired. The surface of the insulating layer 4 was polished, and in order to further improve the flatness, a BaTiO ₃ film having a thickness of 400 nm was formed on the surface by sputtering. Then, anneal in air at 700 ° C. for 3
A substrate with a thick insulating layer having a thickness of 0 μm was obtained.

As shown in FIG. 1, a lower barrier thin film 53A (30 nm) / lower buffer thin film 52A (100 nm) / phosphor thin film 51 (200n) is formed on the substrate with the thick film insulating layer.
m) / upper buffer thin film 52B (100 nm) / upper barrier thin film 53B (70 nm). The value in parentheses is the thickness. The barrier thin film was formed by the EB evaporation method using Al ₂ O ₃ pellets, and the buffer thin film was formed by the EB evaporation method using ZnS pellets. When forming the barrier thin film, the vacuum chamber was evacuated to a pressure of 1 × 10 ⁻⁴ Pa or less, and then the substrate temperature, the film formation rate, and the oxygen gas flow rate during film formation were set to the values shown in Table 1 for vapor deposition. I went.

The phosphor thin film uses barium thioaluminate as a base material and Eu as a luminescent center, and is formed by a multi-source vapor deposition method using two E guns. First, E containing BaS powder added with 5 atomic% of Eu
The B evaporation source and the EB evaporation source containing Al ₂ S ₃ powder were mixed with H ₂
The phosphor thin film was formed on the substrate which was heated to 400 ° C. and rotated by being provided in a vacuum chamber in which S was introduced and simultaneously evaporating from each EB evaporation source. The evaporation rate of each evaporation source was adjusted so that the film formation rate of the phosphor thin film was 1 nm / s. The flow rate of H ₂ S gas was 10 SCCM.

After forming the upper barrier thin film, it was annealed in air at 700 ° C. for 20 minutes to obtain an EL phosphor laminated thin film.

After annealing, the cross section of the EL phosphor laminated thin film was subjected to a composition analysis by EPMA to examine the compositions of the lower barrier thin film and the upper barrier thin film. Atomic ratio of each thin film O / Al
Is shown in Table 1. Table 1 shows the ratio of O / Al of each thin film to the atomic ratio O / Al (= 1.5) in stoichiometric aluminum oxide as O atomic weight.

As a monitor, in the vacuum chamber, the EL phosphor laminated thin film was simultaneously formed on the Si substrate, and then simultaneously annealed. As a result of composition analysis of the phosphor thin film in this laminated thin film by fluorescent X-ray analysis, the atomic ratio (arbitrary unit) in this thin film was: Ba: 8.36, Al: 17.81, O: 3.38, S: 31.15 and Eu: 0.41. _{That, Ba x Al y O z S} w: atomic ratio in Eu is, Al / Ba = y / x = 2.13, O / (S + O) = z / (w + z) = 0.10, (x + 3y / 2) /(Z+w)=1.02. It should be noted that Ba _x on the Si substrate and in the EL element
It has been confirmed in advance that the Al _y O _{z Sw} : Eu thin films have the same composition.

Next, on the EL phosphor laminated thin film, IT
An ITO transparent electrode (upper electrode 3B) having a film thickness of 200 nm was formed at a substrate temperature of 250 ° C. by an RF magnetron sputtering method using an O target to complete an EL element.

Electrodes were extracted from the upper electrode and the lower electrode of this EL device, and a bipolar electric field having a pulse width of 50 μs was applied at 1 kHz to measure the emission characteristics. The results are shown in Table 1.

[0093]

[Table 1]

The effect of the present invention is clear from Table 1. That is, the EL element of the present invention in which the amount of O atoms in the barrier thin film is within the range defined by the present invention has a significantly higher brightness than the EL element having the barrier thin film made of an oxide having a stoichiometric composition. Has been obtained.

For comparison, an EL device was prepared in the same manner as above except that the phosphor thin film was formed alone instead of the EL phosphor laminated thin film, and the light emitting characteristics were evaluated. Was only 5 cd / m ² , and it was confirmed that the brightness of the EL element can be dramatically improved by providing the buffer thin film and the barrier thin film according to the present invention.

When the luminance half life of the EL device of the present invention was evaluated by an acceleration test, it was 30,000 hours. On the other hand, if the thickness of the upper buffer thin film is 40
E having the same structure as the EL element of the present invention except that it is 0 nm.
When the L element was also evaluated in the same manner, the luminance half life was 2000 hours. Further, in the EL element in which the phosphor thin film alone was formed instead of the EL phosphor laminated thin film of the present invention, the luminance half life was only several tens of minutes. From this result, it is understood that the present invention can significantly improve the life characteristics.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration example of an EL phosphor laminated thin film of the present invention.

FIG. 2 is a cross-sectional view showing another structural example of the EL phosphor laminated thin film of the present invention.

FIG. 3 is a cross-sectional view showing another configuration example of the EL phosphor laminated thin film of the present invention.

FIG. 4 is a perspective view showing a part of an EL element cut out.

FIG. 5 is a perspective view showing a part of an EL element having a double insulating structure by cutting out.

[Explanation of symbols]

2 substrates 3A lower electrode 3B upper electrode 4 insulating layers 4A Lower insulating layer 4B Upper insulating layer 5 Light emitting layer 50 EL phosphor laminated thin film 51 Phosphor thin film 52 buffer thin film 52A Lower buffer thin film 52B Upper buffer thin film 53 Barrier thin film 53A Lower barrier thin film 53B Upper barrier thin film

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H05B 33/20 H05B 33/20 F term (reference) 3K007 AB02 AB11 CA01 CA02 CA03 CA04 CB01 DA02 DB01 DC04 EB05 EC01 EC02 FA03 4H001 CA04 XA08 XA12 XA13 XA16 XA20 XA31 XA38 XA49 XA56 YA63

Claims (12)

[Claims] 1. An EL phosphor laminated thin film formed on a substrate, which comprises, from the substrate side, a phosphor thin film containing a host material and an emission center, and a sulfide and having a thickness of 30 to 30. Contains a buffer thin film of 300 nm and oxide, and has a thickness of 5 to 150
A barrier thin film having a thickness of nm is laminated in this order, and the atomic ratio of oxygen in the oxide contained in the barrier thin film is more than 94% and 100% of the atomic ratio of oxygen in the oxide of the stoichiometric composition. An EL phosphor laminated thin film which is less than. 2. The atomic ratio of oxygen in the oxide contained in the barrier thin film is 94.3 to 99.9% with respect to the atomic ratio of oxygen in the oxide having a stoichiometric composition.
EL phosphor laminated thin film. 3. The EL phosphor laminated thin film according to claim 1, wherein a second buffer thin film is provided between the substrate and the phosphor thin film. 4. The E of claim 3, wherein a second barrier thin film is provided between the substrate and the second buffer thin film.
L phosphor laminated thin film. 5. The EL phosphor laminated thin film according to claim 1, wherein the sulfide contained in the buffer thin film is zinc sulfide. 6. The EL phosphor laminated thin film according to claim 1, wherein the oxide contained in the barrier thin film is aluminum oxide. 7. The main component is oxysulfide in which at least one compound selected from alkaline earth thioaluminates, alkaline earth thiogallates and alkaline earth thioindates is substituted with oxygen for part of sulfur. The EL phosphor laminated thin film according to any one of claims 1 to 6, wherein the emission center is a rare earth element. 8. The EL phosphor laminated thin film according to claim 1, wherein the host material and the emission center contained in the phosphor thin film have a composition represented by the following composition formula. Formula _{A x B y O z S w} : in M [the composition formula, A is, Mg, Ca, Sr, Ba
And at least one element selected from rare earth elements,
B is at least 1 selected from Al, Ga and In
X, y, z and w represent atomic ratios, x = 1-5, y = 1-15, z = 0-30 (excluding 0), w = 0-30 (0 Except), and M represents an element serving as a luminescence center.] 9. The EL phosphor laminated thin film according to claim 8, wherein in the composition formula, the relationship between z and w is z / (z + w) = 0.01 to 0.85. 10. The EL phosphor laminated thin film according to claim 8, wherein in the composition formula, the relationship between x and y is y / x = 2.1 to 3.0. 11. The luminescent center is Eu.
10. The EL phosphor laminated thin film of any one of 10. 12. The EL according to any one of claims 1 to 11.
An EL device having a phosphor laminated thin film.