JP3970152B2 - Composite substrate, EL panel using the same, and manufacturing method thereof - Google Patents

Description

【００７０】
表１から明らかなように、最低破壊電圧は、Ｖ−４サンプルの従来構造品に対して、Ｖ−１サンプルで１００Ｖ上昇している。更に２５０Ｖまでの破壊総数では、Ｖ−４サンプルの従来溝造品の３個に対して、本発明構造では、どのサンプルも０個である。この結果は、本発明構造の優位性をはっきりと現している。
【００７１】
Ａ＋Ｂのトータル層数で比較すると、Ａ＋Ｂのトータル膜厚に関係なく、層数が増す毎に、平均破壊電圧が高くなり、最低破壊電圧も高くなっている。このことにより、層数を増やす毎にＥＬパネルの信頼性が向上すると言える。
【００７２】
【発明の効果】
以上のように本発明によれば、厚膜絶縁体層の絶縁性を確保し、そのうえに製膜される発光層等の機能性薄膜の安定した動作、特に安定した発光が可能な複合基板およびＥＬパネルとその製造方法を提供することができる。
【図面の簡単な説明】
【図１】本発明の複合基板の実施態様を示した概略断面図である。
【図２】本発明のＥＬパネルの実施態様を示した概略断面図である。
【図３】実施例の結果を示す駆動時間とＬ／L0の関係を示したグラフである。
【図４】従来のＥＬパネルの溶液塗布焼成法により形成された誘電体層を示した概略断面図である。
【図５】従来のＥＬ素子の基本構成を示した概略断面図である。
【符号の説明】
１ 基板
２ 下部電極
３ 厚膜誘電体層
４ 溶液塗布焼成法により形成された誘電体層
５ 発光層
６ 薄膜絶縁層
７ 透明電極[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a composite substrate used for a light emitting display device and a surface light source and a method for manufacturing the same, and more particularly to an EL panel using a high dielectric constant ceramic layer of an AC drive type EL element as an insulating layer.
[0002]
[Prior art]
The EL element includes a dispersed EL element having a structure in which a powder luminescent material is dispersed in an organic substance or a hollow and electrode layers are provided on the upper and lower sides, two electrode layers and two thin film insulators on an electrically insulating substrate. There is a thin-film EL element using a thin-film light emitter formed in a sandwiched manner. Further, there are a DC voltage driving type and an AC voltage driving type for each driving method. Dispersion EL elements have been known for a long time and have the advantage of being easy to manufacture, but their use has been limited because of their low brightness and short lifetime. On the other hand, thin film EL elements have been widely used in recent years because of their high brightness and long life.
[0003]
FIG. 4 shows a structure of a typical double insulation type thin film EL element as a conventional thin film type EL element. This thin-film EL element is a transparent film formed in a predetermined stripe pattern made of ITO having a film thickness of about 0.2 μm to 1 μm on a transparent substrate 21 such as blue plate glass used for liquid crystal displays and PDPs. The electrode layer 22, the thin film transparent first insulator layer 23, the light emitting layer 24 having a film thickness of about 0.2 μm to 1 μm, and the thin film second insulator layer 25 are laminated, and further stripes so as to be orthogonal to the transparent electrode layer 22. A metal electrode layer 26 such as an Al thin film patterned in a shape is formed. Then, a voltage is selectively applied from a power source 30 to a specific light emitter selected by the matrix of the transparent electrode layer 22 and the metal electrode layer 26 to cause the light emitter of the specific pixel to emit light, and the light emission is transmitted to the substrate 21. Remove from the side. Such thin-film insulator layers 23 and 25 have a function of limiting the current flowing in the light-emitting layer 24, can suppress dielectric breakdown of the thin-film EL element, and provide stable light-emitting characteristics. Works. For this reason, the thin film EL element having this structure is widely used commercially.
[0004]
However, structural problems to be solved still remain in such thin film EL elements. In other words, since the insulator layer is formed of a thin film, there is no defect in the thin film insulator due to the stepped portion of the pattern edge of the transparent electrode or dust generated in the manufacturing process when the display is a large area. However, there is a problem that the light emitting layer is destroyed due to a local decrease in the withstand voltage. Since such defects become a fatal problem as a display device, the thin-film EL element has been a major obstacle to practical application as a large-area display compared to a liquid crystal display or a plasma display. .
[0005]
In order to solve the problem that such a thin film insulator defect occurs, Japanese Patent Publication No. 7-44072 uses an electrically insulating ceramic substrate as a substrate, and uses a thick film instead of the thin film insulator under the light emitter. An EL element using a dielectric is disclosed. Unlike the structure of the conventional thin film EL element, the EL element disclosed in this document takes out light emitted from the light emitter from the upper side opposite to the substrate, and therefore the transparent electrode layer is formed on the upper part.
[0006]
In this EL element, the thick film dielectric layer is formed to have a thickness of several tens to several hundreds of micrometers, which is several hundreds to several thousand times that of the thin film insulator layer. Therefore, the dielectric breakdown at the initial operation due to the pinhole formed by the step of the electrode or the dust in the manufacturing process is very small. By the way, the use of such a thick film dielectric layer causes a problem that the effective voltage applied to the light emitting layer drops. For example, in the above Japanese Patent Publication No. 7-44072, a composite perovskite high dielectric constant material is used as a dielectric. This problem is improved by using the layer.
[0007]
However, the light emitting layer formed on the thick dielectric layer is only a few hundreds of nanometers, which is about 1/100 of the thick dielectric layer. For this reason, the surface of a thick film dielectric layer must be smooth at a level below the thickness of the light emitting layer, but it has been difficult to sufficiently smooth the dielectric surface produced by the normal thick film process. .
[0008]
That is, the thick film dielectric layer is essentially composed of ceramics using a powder raw material. For this reason, when it sinters densely, volume contraction of about 30 to 40% is usually generated. However, while ordinary ceramics shrink in volume three-dimensionally and become dense during sintering, thick-film ceramics formed on the substrate are constrained by the substrate, so in the in-plane direction of the substrate It cannot shrink, and it can shrink volume only in one dimension in the thickness direction. For this reason, sintering of the thick dielectric layer becomes essentially porous without being sufficient. Furthermore, since the surface roughness of the thick film does not become less than the crystal grain size of the polycrystalline sintered body, the surface has an uneven shape of submicron size or more.
[0009]
A light emitting layer formed by a vapor deposition method such as a vapor deposition method or a sputtering method cannot be uniformly formed on the surface of such a dielectric layer. In addition, an electric field cannot be effectively applied to the non-uniform light-emitting layer portion, and the effective light-emitting area is reduced, or the light-emitting layer partially breaks down due to local non-uniformity in film thickness, resulting in light emission. There has been a problem that the brightness is lowered. Further, since the film thickness varies greatly locally, the electric field strength applied to the light emitting layer varies greatly locally, and there is a problem that a clear light emission voltage threshold cannot be obtained.
[0010]
In order to solve such problems, for example, in Japanese Patent Application Laid-Open No. 7-50197, a high dielectric constant layer such as lead zirconate titanate formed by a sol-gel method is formed on a thick film dielectric surface made of lead niobate. A method of stacking and improving the flatness of the surface is disclosed. That is, as shown in FIG. 5, after the electrode 12 is formed on the substrate 11 and the thick dielectric layer 13 is formed, the planarization layer 14 such as lead zirconate titanate formed by the sol-gel method is formed. , Improving the surface flatness.
[0011]
However, when a planarizing layer is formed on the surface of a thick film dielectric layer that is several tens to several hundreds of micrometers and is a porous body, minute cracks are generated in the planarizing layer. In the portion where the crack is generated, the insulating property is lowered, so that stable operation over a long period of time becomes difficult.
[0012]
[Problems to be solved by the invention]
An object of the present invention is to provide a composite substrate and an EL panel capable of ensuring the insulation of a thick dielectric layer and stable operation of a functional thin film such as a light emitting layer formed thereon, in particular, stable light emission, and the manufacture thereof. Is to provide a method.
[0013]
[Means for solving the problems]
That is, the above object is achieved by the following present invention configuration.
(1) At least a substrate, an electrode formed on the substrate, and a thick film dielectric layer formed on the electrode by a thick film method , the thick film dielectric layer and the thick film dielectric A dielectric layer formed by a solution coating and firing method is formed below the body layer and / or between the thick film dielectric layers, and the dielectric layer formed by the solution coating and firing method is a thick film dielectric layer A composite substrate for an EL panel, in which a plurality of dielectric layers formed by this solution coating and baking method are 2 to 5 layers .
( 2 ) An EL panel having at least a light emitting layer and another electrode layer on a dielectric layer formed by a solution coating firing method on a thick film dielectric layer of the composite substrate for EL panel.
(3) and at least a substrate, a the electrode formed on the substrate, a manufacturing method of a composite substrate having a thick film dielectric layer formed by the thick film method on the electrode, the thick film dielectric A dielectric layer is formed by a solution coating and firing method on the layer and under the thick film dielectric layer and / or between the thick film dielectric layers, and the dielectric layer formed by the solution coating and firing method is a thick film dielectric. A method of manufacturing a composite substrate for an EL panel, wherein a plurality of layers are formed via a body layer, and the total number of dielectric layers formed by the solution coating and firing method is 2 to 5 layers .
[0014]
DETAILED DESCRIPTION OF THE INVENTION
The composite substrate of the present invention is formed by at least a substrate, an electrode formed on the substrate, a thick dielectric layer formed on the electrode, and a solution coating firing method on the thick dielectric layer. The thick dielectric layer and the dielectric layer formed by a solution coating and firing method are alternately formed in a plurality of layers.
[0015]
Thus, by having a dense dielectric layer formed by a solution coating and firing method between the thick film dielectric layer and the thick film dielectric layer, the thick film dielectric layer is formed. When the insulating properties of the layers can be secured and a functional thin film such as a light emitting layer is formed thereon, stable operation and light emission can be obtained over a long period of time. That is, the voltage applied between the internal electrode and the thin film such as the light emitting layer can be stabilized. As a result, the device becomes stable and the reliability is improved.
[0016]
When a dielectric material solution is applied onto the thick film dielectric layer, the dielectric material solution soaks to a certain depth above the thick film dielectric layer due to capillary action or the like, and the thick film dielectric layer in the soaked area Between the crystal grains. Subsequent firing causes the organic component of the dielectric material solution to burn and vaporize, resulting in volume shrinkage, but the dielectric formed by the solution coating firing method fills part of the crystal grains of the thick film dielectric layer. A high density region is formed to a certain depth above the thick dielectric layer. Therefore, according to the present invention, when the dense dielectric layer is formed on the thick film dielectric layer by the solution coating firing method, the above-described phenomenon has the effect of increasing the density of the upper region of the underlying thick film dielectric layer. Needless to say.
[0017]
In other words, when forming a dielectric by a solution coating and firing method on a thick film dielectric layer, the dielectric material solution is adjusted so as to fill the gaps between the crystal grains of the thick film dielectric layer by adjusting the viscosity or coating amount of the dielectric material solution. can do. In this case, although the layer structure is not clear, the effect of the present invention can be obtained by forming a dielectric by a solution coating firing method on the thick film dielectric layer and densifying the thick film dielectric layer. It is done. Therefore, the dielectric layer obtained by the solution coating firing method defined in the present invention includes those integrated with the thick film dielectric layer in this way.
[0018]
A composite laminate of a thick film dielectric layer and a dielectric layer formed by a solution coating and firing method is preferable as the number of layers of the composite laminate increases the insulation and stability. However, when the number of dielectric layers formed by the solution coating and firing method is increased, the process becomes complicated and the cost of the product is increased. Therefore, the preferred number of layers is 2 to 5 layers, particularly 2 to 3 layers.
[0019]
The composite substrate of the present invention may have a structure as shown in FIG. That is, a lower electrode layer 2 formed in a predetermined pattern on a substrate 1 having electrical insulation, a thick film dielectric layer 3a, 3b and a dielectric layer 4a formed by a solution coating firing method on the lower electrode layer 2. It is a laminated body with 4b. Although not shown in the illustrated example, the dielectric layer formed by the solution coating and firing method may be formed under the thick film dielectric layer 3a.
[0020]
The substrate is not particularly limited as long as it has electrical insulation and can maintain a predetermined heat resistance without contaminating the lower electrode layer and the dielectric layer formed thereon.
[0021]
Specific materials include alumina (Al ₂ O ₃ ), quartz glass (SiO ₂ ), magnesia (MgO), forsterite (2MgO · SiO ₂ ), steatite (MgO · SiO ₂ ), mullite (3Al ₂ O ₃ · 2SiO ₂ ), beryllia (BeO), zirconia (ZrO ₂ ), aluminum nitride (AlN), silicon nitride (SiN), silicon carbide (SiC) and other ceramic substrates, crystallized glass, high heat resistant glass, etc. It is also possible to use a metal substrate or the like that has been subjected to a brazing process.
[0022]
When the display device is a simple matrix type, the lower electrode layer is formed to have a plurality of stripe patterns. Further, since the line width is one pixel and the space between the lines is a non-light emitting region, it is preferable to make the space between the lines as small as possible. Specifically, although it depends on the resolution of the target display, for example, a line width of 200 to 500 μm and a space of about 20 to 50 μm are required.
[0023]
A material for the lower electrode layer is preferably a material that has high conductivity, is not damaged when the dielectric layer is formed, and has low reactivity with the dielectric layer and the light emitting layer. Such lower electrode layer materials include noble metals such as Au, Pt, Pd, Ir, and Ag, noble metal alloys such as Au—Pd, Au—Pt, Ag—Pd, and Ag—Pt, and Ag—Pd—Cu. An electrode material having a precious metal such as a main component and a base metal element added is preferable because oxidation resistance to an oxidizing atmosphere during firing of the dielectric layer can be easily obtained. In addition, an oxide conductive material such as ITO, SnO ₂ (nesa film), ZnO—Al, or the like may be used. Further, a base metal such as Ni or Cu is used, and the oxygen partial pressure when firing the dielectric layer is set. These base metals can also be used in a range where they are not oxidized.
[0024]
As a method for forming the lower electrode layer, a known technique such as sputtering, vapor deposition, or plating may be used.
[0025]
The thick film dielectric layer needs to have a high dielectric constant and a high withstand voltage, and is required to be a material that can be fired at a low temperature in consideration of the heat resistance of the substrate.
[0026]
Here, the thick film dielectric layer is a ceramic layer formed by firing a powdery insulator material by a so-called thick film method. The thick film dielectric layer is formed, for example, by printing and baking an insulator paste prepared by mixing a binder and a solvent with a powdery insulator material on a substrate on which a lower electrode layer is formed. be able to. Alternatively, a green sheet may be formed by casting an insulating paste to form a laminate.
[0027]
The conditions for the binder removal treatment performed before firing may be normal.
[0028]
The atmosphere during firing may be appropriately determined according to the type of the lower electrode material. However, when firing in an oxidizing atmosphere, ordinary firing in the air may be performed.
[0029]
The firing temperature may be appropriately determined according to the material of the thick film dielectric layer, but is usually about 700 to 1200 ° C., preferably 1000 ° C. or less. The firing time is preferably 0.05 to 5 hours, particularly preferably 0.1 to 3 hours.
[0030]
Moreover, you may anneal-treat as needed.
[0031]
The film thickness of the thick film dielectric layer is required to be thick in order to eliminate pinholes formed by electrode steps or dust in the manufacturing process, etc., and the total thickness of the thick film dielectric layer in the entire laminate is at least It is 10 μm or more, preferably about 15 to 20 μm.
[0032]
The material for the thick film dielectric layer is preferably a high dielectric constant ceramic composition that can be formed at a low temperature in consideration of the heat resistance limitation of the substrate material.
[0033]
For example, a dielectric having a perovskite structure such as BaTiO ₃ , (Ba _x Ca _1-x ) TiO ₃ , (Ba _x Sr _1-x ) TiO ₃ , PbTiO ₃ , Pb (Zr _x Ti _1-x ) O ₃ , strong Dielectric materials, composite perovskite relaxor type ferroelectric materials represented by Pb (Mg _1/3 Ni _2/3 ) O ₃ , Bi ₄ Ti ₃ O ₁₂ , SrBi ₂ Ta ₂ O ₉ A tungsten bronze ferroelectric material such as bismuth layered compound, (Sr _x Ba _1-x ) Nb ₂ O ₆ , PbNb ₂ O _6, etc. is preferable because of its high dielectric constant and easy firing.
[0034]
The dielectric material containing lead in the composition has a low melting point of lead oxide as low as 888 ° C., and lead oxide and other oxide materials such as SiO ₂ , CuO, Bi ₂ O ₃ , Fe ₂ O _3. Since a liquid phase is formed at a low temperature of about 700 ° C. to 800 ° C., etc., firing is easy at a low temperature and a high dielectric constant is easily obtained, which is preferable. For example, a perovskite structure dielectric material such as Pb (Zr _x Ti _1-x ) O _3, a composite perovskite relaxor type ferroelectric material typified by Pb (Mg _1/3 Ni _2/3 ) O ₃ , PbNb Examples include tungsten bronze ferroelectric materials represented by ₂ O _{6 and the} like. These can easily form a dielectric having a relative dielectric constant of 1000 to 10,000 at a firing temperature of 800 to 900 ° C., which is the upper limit heat resistance temperature of a normal ceramic substrate such as alumina ceramics.
[0035]
When forming the dielectric layer formed by the solution coating and baking method, the precursor solution used in the solution coating and baking method is a metal organic compound of a metal element constituting the dielectric layer, or a metal alkoxide and these metal source elements. It is composed of an organic complex in solution and a volatile solvent.
[0036]
The solution coating and firing method refers to a method in which a dielectric material precursor solution such as a sol-gel method or a MOD method is applied to a substrate and a dielectric layer is formed by firing.
[0037]
In the sol-gel method, generally, a predetermined amount of water is added to a metal alkoxide dissolved in a solvent, and a precursor solution of a sol having an MOM bond formed by hydrolysis and polycondensation reaction is applied to a substrate and baked. This is a method for forming a film. The MOD (Metal-Organic Decomposition) method forms a film by dissolving a metal salt of a carboxylic acid having an MO bond in an organic solvent to form a precursor solution, and applying and baking the substrate. Is the method. Here, the precursor solution refers to a solution containing an intermediate compound produced by dissolving a raw material compound in a solvent in a film forming method such as a sol-gel method or a MOD method.
[0038]
The sol-gel method and the MOD method are not completely separate methods and are generally used in combination with each other. For example, when forming a PZT film, it is common to use lead acetate as the Pb source and adjust the solution using the alkoxide as the Ti and Zr sources. In addition, the two methods of the sol-gel method and the MOD method may be collectively referred to as the sol-gel method, but in any case, a film is formed by applying a precursor solution to a substrate and baking it. Then, it is set as the solution application baking method. Moreover, even if the solution is a mixture of submicron-sized dielectric particles and a dielectric precursor solution, it is included in the dielectric precursor solution of the present invention, and the solution is applied to a substrate and fired. It is included in the solution coating firing method of the present invention.
[0039]
In the solution coating and firing method, both the sol-gel method and the MOD method use ceramic powder sintering essentially like the dielectric formation by the thick film method because the elements constituting the dielectric are uniformly mixed. Compared with the conventional technique, it is characterized in that a dense dielectric can be synthesized at an extremely low temperature.
[0040]
The biggest purpose of the solution coating and baking method is that the dielectric layer formed by this method is formed through a process of applying and baking the precursor solution, so that the concave portion of the substrate is thick and convex A thin layer is formed. In addition, the thick film dielectric layer enters a fine hole, penetrates into the thick film dielectric layer, and the entire thick film dielectric layer becomes dense.
[0041]
The thickness of the dielectric layer formed by the solution coating and firing method is 0.5 μm or more, preferably 1 μm or more in order to sufficiently flatten the unevenness of the thick film surface. In addition, when it is formed on the base of the thick film dielectric layer or inside, it is preferably about 0.01 to 1 μm. It should be noted that the lower limit of the film thickness is that the coating solution is thick in the concave portion of the substrate as described above, and a thin layer is formed in the convex portion, and enters the fine holes of the thick dielectric layer, and the thick film dielectric. Since it penetrates to the inside of the body layer, in an extreme case, it is only necessary to confirm a trace enough to fill the concave portion of the surface unevenness. Therefore, the above lower limit value is only a guideline, and it suffices if the region has a thickness enough to confirm that the dielectric layer formed by the solution coating firing method is formed, or a region where a part thereof can be confirmed.
[0042]
The film formation method of the solution coating and baking method is to form a precursor layer on the substrate by applying the precursor solution to the substrate by spin coating, dip coating, spray coating, or the like, and then the precursor By firing the layer, the organic component in the precursor is removed, an ultrafine oxide layer is formed by the combination of the metal element and oxygen, and this oxide is fired to form the dielectric layer.
[0043]
The dielectric layer formed by the solution application baking method needs to have a high dielectric constant. Examples of the high dielectric constant material include perovskites such as BaTiO ₃ , (Ba _x Ca _1-x ) TiO ₃ , (Ba _x Sr _1-x ) TiO ₃ , PbTiO ₃ , and Pb (Zr _x Ti _1-x ) O _3. Dielectrics having structure, ferroelectric materials, composite perovskite relaxor type ferroelectric materials represented by Pb (Mg _1/3 Ni _2/3 ) O ₃ , Bi ₄ Ti ₃ O ₁₂ , SrBi ₂ Ta Examples thereof include bismuth bismuth layered compounds represented by ₂ O ₉ (Sr _x Ba _1-x ) Nb ₂ O ₆ , tungsten bronze ferroelectric materials represented by PbNb ₂ O _{6 and the} like. Among these, a ferroelectric material having a perovskite structure such as BaTiO ₃ or PZT is preferable because it has a high dielectric constant and can be easily formed at a relatively low temperature.
[0044]
In order to obtain an EL panel using the composite substrate of the present invention, for example, a structure as shown in FIG. This EL panel includes a lower electrode layer 2 formed in a predetermined pattern on a substrate 1 having electrical insulation, and a dielectric formed by thick film dielectric layers 3a and 3b and a solution coating firing method thereon. The light emitting layer 5, the thin film insulator layer 6, and the transparent electrode layer 7 are laminated | stacked on the laminated body of layers 4a and 4b further. Note that the thin film insulator layer 6 may be formed between the light emitting layer and the dielectric layer formed by the solution coating and baking method, or may be omitted. The lower electrode layer 2 and the upper transparent electrode layer 7 are formed in stripes in directions orthogonal to each other. Then, the arbitrary lower electrode layer 2 and the upper transparent electrode layer 7 are selected, respectively, and light is emitted from a specific pixel by selectively applying a voltage from the AC power source / pulse power source 10 to the light emitting layer at the orthogonal part of both electrodes. Obtainable.
[0045]
Although it does not specifically limit as a material of a light emitting layer, Well-known materials, such as ZnS which doped Mn mentioned above, can be used. Among these, SrS: Ce is particularly preferable because excellent characteristics can be obtained. The thickness of the light emitting layer is not particularly limited, but if it is too thick, the driving voltage increases, and if it is too thin, the light emission efficiency decreases. Specifically, although it depends on the light emitting material, it is preferably about 100 to 2000 nm.
[0046]
As a method for forming the light emitting layer, a vapor deposition method can be used. As the vapor deposition method, a physical vapor deposition method such as sputtering or vapor deposition or a chemical vapor deposition method such as CVD is preferable. In particular, when a light emitting layer of SrS: Ce is formed, high purity light emission is obtained by forming the substrate temperature during film formation from 500 ° C. to 600 ° C. by electron beam evaporation in an H ₂ S atmosphere. It is possible to obtain a layer.
[0047]
After the light emitting layer is formed, heat treatment is preferably performed. Heat treatment may be performed after laminating the electrode layer, dielectric layer, and light emitting layer from the substrate side, or the electrode layer, dielectric layer, light emitting layer, insulator layer, or electrode layer is formed on the substrate side from the substrate side. After that, heat treatment may be performed. The temperature of the heat treatment depends on the light emitting layer to be formed, but is preferably 300 ° C. or higher, more preferably 400 ° C. or higher, which is lower than the firing temperature of the dielectric layer. The treatment time is preferably 10 to 600 minutes. The atmosphere during the heat treatment may be selected from air, N ₂ , He, Ar, and the like depending on the composition and formation conditions of the light emitting layer.
[0048]
The insulator layer functions as a function of adjusting the electronic state of the interface between the light emitting layer and the dielectric layer to stabilize and improve the electron injection into the light emitting layer, and this electronic state is on both sides of the light emitting layer. The main objective is to improve the positive / negative symmetry of the light emission characteristics during AC drive by configuring symmetrically, and it is not necessary to consider the function of maintaining the dielectric strength, which is the role of the dielectric layer, so the film thickness Can be small.
[0049]
The insulator layer preferably has a resistivity of 10 ⁸ Ω · cm or more, particularly about 10 ¹⁰ to 10 ¹⁸ Ω · cm. Moreover, it is preferable that it is a substance which has a comparatively high dielectric constant, and the dielectric constant is preferably 3 or more. Examples of the constituent material of the insulator layer include silicon oxide (SiO ₂ ), silicon nitride (SiN), tantalum oxide (Ta ₂ O ₅ ), yttrium oxide (Y ₂ O ₃ ), zirconia (ZrO ₂ ), silicon oxy Nitride (SiON), alumina (Al ₂ O ₃ ), or the like can be used. As a method for forming the insulator layer, a sputtering method, a vapor deposition method, or a CVD method can be used. The thickness of the insulator layer is preferably about 10 to 1000 nm, particularly preferably about 20 to 200 nm.
[0050]
The transparent electrode layer is made of an oxide conductive material such as ITO, SnO ₂ (nesa film), ZnO—Al having a film thickness of 0.2 μm to 1 μm. As a method for forming the transparent electrode layer, a known technique such as vapor deposition as well as sputtering may be used.
[0051]
Although the above-described EL element has only a single light emitting layer, the EL element of the present invention is not limited to such a configuration, and a plurality of types of light emitting layers may be stacked in the film thickness direction. Alternatively, different types of light emitting layers (pixels) may be arranged in a plane on the same surface.
[0052]
【Example】
[Example 1]
On a 96% purity alumina substrate, an Au thin film added with a trace amount of additive was formed by sputtering to a thickness of 1 μm and stabilized by heat treatment at 850 ° C. This Au lower electrode layer was patterned into a large number of stripes having a width of 300 μm and a space of 30 μm by using a photoetching method.
[0053]
A dielectric ceramic thick film was further formed on the substrate on which the lower electrode was formed by screen printing. As the thick film paste, ESL 4210C thick film dielectric paste was used, and screen printing and drying were repeated so that the film thickness after firing was 5 μm.
[0054]
After printing and drying, the thick film was baked at 850 ° C. for 20 minutes in an atmosphere supplied with sufficient air using a belt furnace.
[0055]
Next, a dielectric layer was formed on the substrate using a solution coating and firing method. A PZT sol-gel solution prepared by the following method was prepared as a method for forming a dielectric layer by a solution coating and baking method, and used as a solution coating and baking method precursor solution. First, the operation of applying the precursor solution to the substrate by spin coating and baking at 700 ° C. for 15 minutes was repeated a predetermined number of times.
[0056]
The basic sol-gel solution was prepared by heating and stirring 8.49 g of lead acetate trihydrate and 4.17 g of 1.3 propanediol for about 2 hours to obtain a transparent solution. Separately, 3.70 g of zirconium / normal propoxide 70 mass%, 1-propanol solution and 1.58 g of acetylacetone were heated and stirred in a dry nitrogen atmosphere for 30 minutes, and 3.14 g of titanium Isopropoxide bisacetylacetonate 75 mass%, 2-propanol solution and 2.32 g of 1.3 propanediol were added, and the mixture was further heated and stirred for 2 hours. These two solutions were mixed at 80 ° C., and heated and stirred in a dry nitrogen atmosphere for 2 hours to prepare a brown transparent solution. By keeping this solution at 130 ° C. for several minutes, by-products were removed, and the mixture was further heated and stirred for 3 hours to prepare a PZT precursor solution.
[0057]
The viscosity of the PZT precursor solution was adjusted by diluting with n-propanol. The thickness of the dielectric layer per single layer was adjusted by adjusting the spin coating conditions and the viscosity of the sol-gel solution, and repeating the application and firing by spin coating to form a PZT dielectric layer having a thickness of about 1 μm. .
[0058]
The same operation is repeated, and a thick film dielectric layer 10 μm and a dielectric layer 1 μm formed by a solution coating firing method are respectively laminated, and a thick film dielectric layer 5 μm / dielectric layer 1 μm / A thick film dielectric layer 10 μm / dielectric layer 1 μm formed by a solution coating firing method was used. This laminate had a relative dielectric constant of about 2500.
[0059]
The light-emitting layer was formed by a vacuum evaporation method using a ZnS vapor deposition source doped with Mn while being heated to 200 ° C. to a film thickness of 0.8 μm, and then heat-treated at 600 ° C. for 10 minutes in a vacuum. did.
[0060]
Next, an EL element was formed by sequentially forming 0.1 μm of a Si ₃ N ₄ thin film as an insulator layer and 0.5 μm of an ITO thin film as an upper electrode layer by sputtering. At that time, the ITO thin film of the upper electrode layer was patterned into a large number of stripes having a line width of 1 mm and a space of 0.5 mm by using a metal mask during film formation.
[0061]
Further, as a comparative sample, a sample was formed in which a thick film dielectric layer was 30 μm and a dielectric layer formed by a solution coating and baking method was about 3 μm, and each one layer was formed.
[0062]
Electrodes were drawn from the lower electrode and the upper transparent electrode of the obtained element structure and operated at 25 ° C. with a 1 kHz pulse width of 50 μs and a voltage of 180 V, and the relative luminance characteristics L / L ₀ during continuous driving were measured. Here, L ₀ is the luminance at the start of voltage application. The present invention sample and comparison sample 3, in which was sealed at atmospheric pressure in the following N ₂ atmosphere. That is, it is an EL panel in which the space sealed with the sealing glass in the EL panel is made an N ₂ atmosphere at atmospheric pressure or lower. In the same manner, the one sealed in the N ₂ atmosphere at atmospheric pressure is shown in Comparative Example 1, and the EL panel that does not seal with the desiccant on the shrink tube (glass tube) larger than the sealed space. Then, after performing N ₂ gas replacement, the pressure was reduced to atmospheric pressure or lower, and this was designated as Comparative Example 2. The results are shown in FIG.
[0063]
In FIG. 3, the operation time when converted to a drive frequency of 75 Hz as the horizontal axis (X axis), and the relative characteristic value of the light emission luminance are attached to the vertical axis (Y axis). Further, the value 1 shown on the horizontal axis represents the voltage application start time. As is clear from the figure, the sample of the present invention is superior to the comparison 1 having the best characteristics among the comparative samples, and there is almost no deterioration in luminance.
[0064]
[Example 2]
In order to perform a withstand voltage test of the composite substrate of the present invention, a sample having the following configuration was prepared.
Alumina substrate / lower Au electrode / composite thick film dielectric (structure of the present invention) / upper ITO electrode.
[0065]
The lower Au electrode and the upper ITO electrode had the same shape as in Example 1, and the number of lines was 80 and 70, respectively.
[0066]
The composite thick film dielectric was formed as follows. Here, the thick-film dielectric layer is represented as A, and the solution-coated dielectric layer is represented as B, and are described from the left in the order of lamination.
V-1 sample: A-5 μm / B-1 μm / A-10 μm / B-1 μm
V-2 sample: B-0.3 μm / A-5 μm / B-0.1 μm / A-10 μm / B-1 μm
V-3 sample: A-5 μm / B-0.1 μm / A-5 μm / B-0.1 μm / A-5 μm / B-1 μm
[0067]
Furthermore, as a comparative example of the above sample, a V-4 sample having a conventional structure (conventional structure): A-20 μm / B-1 μm
Was made.
[0068]
The withstand voltage test was performed using a withstand voltage tester-TOS5052 manufactured by Kikusui Electronics Corporation. Conditions are as follows: for 80 lines of the lower Au electrode and for each line of the upper ITO electrode, each voltage is held for 3 seconds in 10V increments under the condition of sine wave and 60 Hz, and the voltage is raised stepwise. Measurement was performed by setting a voltage at which a current of 0 mA flowed as a breakdown voltage. Table 1 shows the average breakdown voltage, the minimum breakdown voltage, etc. of 70 samples.
[0069]
[Table 1]

[0070]
As is clear from Table 1, the minimum breakdown voltage is increased by 100 V in the V-1 sample with respect to the conventional structure product of the V-4 sample. Furthermore, in the total number of breakdowns up to 250V, the number of samples in the structure of the present invention is zero for three of the conventional grooved structures of V-4 samples. This result clearly shows the superiority of the structure of the present invention.
[0071]
When compared with the total number of layers of A + B, the average breakdown voltage increases and the minimum breakdown voltage increases as the number of layers increases, regardless of the total film thickness of A + B. Thus, it can be said that the reliability of the EL panel is improved every time the number of layers is increased.
[0072]
【The invention's effect】
As described above, according to the present invention, a composite substrate and an EL that can ensure the insulation of the thick insulator layer and can stably operate a functional thin film such as a light emitting layer formed thereon, in particular, stable light emission. A panel and a manufacturing method thereof can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing an embodiment of a composite substrate of the present invention.
FIG. 2 is a schematic cross-sectional view showing an embodiment of an EL panel according to the present invention.
FIG. 3 is a graph showing the relationship between drive time and L / L0 showing the results of the example.
FIG. 4 is a schematic sectional view showing a dielectric layer formed by a solution coating and firing method of a conventional EL panel.
FIG. 5 is a schematic cross-sectional view showing a basic configuration of a conventional EL element.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Substrate 2 Lower electrode 3 Thick film dielectric layer 4 Dielectric layer 5 formed by solution coating and baking method Light emitting layer 6 Thin film insulating layer 7 Transparent electrode

Claims (3)

Having at least a substrate, an electrode formed on the substrate, and a thick film dielectric layer formed on the electrode by a thick film method ,
A dielectric layer formed by a solution coating and firing method is formed on the thick film dielectric layer and below the thick film dielectric layer and / or between the thick film dielectric layer ,
A plurality of dielectric layers formed by the solution coating and baking method are formed through thick film dielectric layers, and the total number of dielectric layers formed by this solution coating and baking method is 2 to 5 layers. Composite panel for EL panel . 2. An EL panel having at least a light emitting layer and another electrode layer on a dielectric layer formed by a solution coating firing method on a thick dielectric layer of the composite substrate for an EL panel according to claim 1 . And at least a substrate, a the electrode formed on the substrate, a manufacturing method of a composite substrate having a thick film dielectric layer formed by the thick film method on the electrode,
Forming a dielectric layer on the thick dielectric layer and under the thick dielectric layer and / or between the thick dielectric layers by a solution coating and baking method ;
A plurality of dielectric layers formed by the solution coating and baking method are formed through thick film dielectric layers, and the total number of dielectric layers formed by this solution coating and baking method is 2 to 5 layers. Manufacturing method of composite substrate for EL panel .

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