JP2002246180A - El element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent peeling and breakages of the lower electrode layer, due to addition of a sol-gel dielectric layer in an EL element for securing surface evenness of a thick film ceramic dielectric layer, by means of the sol-gel dielectric film for providing a highly reliable EL element which has no defects. SOLUTION: This EL element is constructed by layering at least an electrical insulative base board, an electrode layer having a pattern on the base board, a dielectric layer covering the electrode layer partially, and a light-emitting layer and a transparent electrode layer laminated on the dielectric layer. The dielectric layer has a multilayer structure, consisting of a thick film and a dielectric layer formed by a solution coating baking method and at least a buffer layer is arranged on the electrode layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an EL element having at least a structure having an electrically insulating substrate, an electrode layer having a pattern on the substrate, a dielectric layer, a light emitting layer and a transparent electrode layer laminated on the electrode layer. .

[0002]

2. Description of the Related Art An EL element is a liquid crystal display (LCD).
It is used as a backlight for watches and watches.

[0003] An EL element is a phenomenon in which a substance emits light when an electric field is applied, that is, electroluminescence (E).
L) An element applying the phenomenon.

[0004] The EL element includes a dispersion type EL element having a structure in which a powder luminous body is dispersed in an organic substance or an enamel, and an electrode layer is provided on the upper and lower sides, and two electrode layers are formed on an electrically insulating substrate.
There is an EL element using a thin-film light-emitting body formed between two thin-film insulators. Further, there are a DC voltage driving type and an AC voltage driving type depending on the driving method. Dispersion-type EL elements have been known for a long time and have an advantage of being easy to manufacture, but their use is limited because of their low luminance and short life. On the other hand, EL elements have been widely used in recent years because of their characteristics of high luminance and long life.

FIG. 9 shows the structure of a typical double insulating thin film EL device as a conventional EL device. This thin-film EL element is formed on a transparent substrate 31 such as blue plate glass used for a liquid crystal display, a PDP, or the like, in a thickness of 0.2 μm to 1 μm.
m, a transparent electrode layer 32, a thin-film transparent first insulator layer 33, a light-emitting layer 34 having a thickness of about 0.2 μm to 1 μm, and a thin-film transparent second insulator. And a metal electrode layer 36 such as an Al thin film patterned in a stripe shape so as to be orthogonal to the transparent electrode layer 32. Then, a voltage is selectively applied from a power source 40 to a specific luminous element selected in the matrix of the transparent electrode layer 32 and the metal electrode layer 36 to cause the luminous element of the specific pixel to emit light, and the light emission is applied to the substrate 31. Take out from the side. Such thin-film insulator layers 33 and 35 have a function of restricting a current flowing in the light-emitting layer 34, can suppress dielectric breakdown of the thin-film EL element, and provide stable light-emitting characteristics. Works. For this reason, the thin film EL device having this structure has been widely and practically used in commerce.

The above-mentioned thin film transparent insulator layers 33 and 35 are usually formed of a transparent dielectric thin film such as Y ₂ O ₃ , Ta ₂ O ₅ , Ai ₃ N ₄ , BaTiO ₃ by sputtering or vapor deposition.
Each is formed with a film thickness of about 1 to 1 μm.

As a light emitting material, Mn which emits yellow-orange light is used.
ZnS to which is added has been mainly used from the viewpoint of ease of film formation and light emission characteristics. In order to produce a color display, it is indispensable to use a luminescent material which emits light in three primary colors of red, green and blue. Examples of these materials include ZnS to which SrS or Tm to which blue light emitting Ce is added, ZnS to which Sm to which red light emitting Sm is added, and Ca to which Eu is added.
Known are S, ZnS to which Tb emitting green light is added, and CaS to which Ce is added.

Also, Monthly Display '98 April issue
"Recent Display Technology Trends", Tanaka, p1-10
Include ZnS, Mn / Cd as materials for obtaining red light emission.
As a material for obtaining green light emission such as SSe, ZnS: TbO
F, ZnS: Tb and other materials for obtaining blue light emission
SrS: Cr, (SrS: Ce / ZnS) n, Ca
_TwoGa_TwoS_Four: Ce, Sr_TwoGa_TwoS_Four: Light emitting material such as Ce
Is disclosed. Also, to obtain white light emission,
Light emitting materials such as SrS: Ce / ZnS: Mn have been disclosed.
I have.

Further, among the above materials, SrS: Ce is used for a thin film EL device having a blue light emitting layer.
(International Display Workshop) '97 X.Wu "Mul
ticolor Thin-Film Ceramic Hybrid EL Displays "p593
to 596. Furthermore, this document includes Sr
It is disclosed that when a light emitting layer of S: Ce is formed by an electron beam evaporation method in an H ₂ S atmosphere, a light emitting layer of high purity can be obtained.

However, such a thin film EL device still has a structural problem to be solved. In other words, since the insulator layer is formed of a thin film, when the display has a large area, the defect of the thin film insulator due to the step portion of the pattern edge of the transparent electrode or dust generated in a manufacturing process is eliminated. However, there is a problem that the light-emitting layer is destroyed due to a local decrease in withstand voltage. Since such a defect is a fatal problem as a display device, the thin-film EL element has been a major obstacle to widespread practical use as a large-area display as compared with a liquid crystal display or a plasma display. .

In order to solve such a problem that the defect of the thin film insulator is generated, Japanese Patent Publication No. 7-44072 discloses that an electrically insulating ceramic substrate is used as a substrate, and instead of the thin film insulator below the light emitting body. E using thick film dielectric
An L element is disclosed. E disclosed in this document
The L element differs from the structure of the conventional thin film EL element in that the light emission of the light emitter is extracted from the upper side opposite to the substrate, so that the transparent electrode layer is formed on the upper side.

Further, in this EL device, the thick dielectric layer is several tens to several hundreds of micrometers, and the thin dielectric layer is several hundreds to several tens of micrometers.
It is formed to a thickness of 00 times. Therefore, there is very little dielectric breakdown due to pinholes formed due to steps of the electrodes or dusts in the manufacturing process, and there is an advantage that high reliability and high yield in manufacturing can be obtained.
By the way, the use of such a thick dielectric layer causes a problem that the effective voltage applied to the light emitting layer is reduced. For example, in Japanese Patent Publication No. 7-44072, a composite perovskite high dielectric constant material is used for the dielectric layer. This problem has been improved by using this method.

However, the light emitting layer formed on the thick dielectric layer has a thickness of only several hundred nm, which is about 1/100 of the thickness of the thick dielectric layer. For this reason, the surface of the thick-film dielectric layer must be smooth at a level equal to or less than the thickness of the light-emitting layer, but it has been difficult to sufficiently smooth the dielectric surface produced by the ordinary thick-film process. .

That is, the thick film dielectric layer is essentially made of ceramics using a powder raw material. For this reason,
Dense sintering usually causes a volume shrinkage of about 30 to 40%. However, while normal ceramics shrink in volume by three-dimensional volume shrinkage during sintering, the thick-film ceramics formed on the substrate are constrained by the substrate, so that Cannot shrink, and can only shrink one-dimensionally in the thickness direction. For this reason, the sintering of the thick film dielectric layer becomes essentially porous with insufficient sintering.
Further, since the surface roughness of the thick film does not become smaller than the crystal grain size of the polycrystalline sintered body, the surface thereof becomes uneven with a submicron size or more.

If the surface of such a dielectric layer has a defect, a porous film quality, or an irregular shape, the light emitting layer formed thereon by a vapor deposition method such as a vapor deposition method or a sputtering method may be used. It cannot be formed uniformly following the shape.
For this reason, an electric field cannot be effectively applied to the light emitting layer portion formed on such a non-flat portion of the substrate, and the light emitting layer is reduced due to a decrease in the effective light emitting area or local unevenness of the film thickness. There has been a problem that the dielectric breakdown occurs partially and the emission luminance is reduced. Furthermore, since the film thickness locally fluctuates greatly, the intensity of the electric field applied to the light emitting layer fluctuates greatly locally, and there is a problem that a clear light emitting voltage threshold cannot be obtained.

In order to solve such a problem, for example, Japanese Unexamined Patent Publication No. 7-50197 discloses a high dielectric material such as lead zirconate titanate formed by a sol-gel method on the surface of a thick film dielectric made of lead niobate. There is disclosed a method for improving the flatness of the surface by laminating a rate layer.

As described above, by using the ceramic high dielectric constant dielectric thick film, it is possible to avoid the step of the pattern edge of the lower electrode layer and the defect of the thin film insulator due to dust and the like generated in the manufacturing process, and to locally prevent the defect. It is possible to solve the problem that the light emitting layer is destroyed due to an excessively low dielectric breakdown voltage.

However, when such a sol-gel method is used, a sol-gel film is also formed at a portion where the lower electrode of the thick ceramic dielectric layer is taken out of the thick film pattern portion. The sol-gel dielectric layer formed on the electrode portion is liable to cause high-density cracks during firing and peeling of the electrodes due to the cracks, which may cause disconnection of the underlying electrode, which is a practical problem. Was.

[0019]

SUMMARY OF THE INVENTION An object of the present invention is to provide an EL device in which the surface flatness of a thick-film ceramic dielectric layer is ensured by a sol-gel dielectric layer. An object of the present invention is to provide a highly reliable EL element free from defects by preventing peeling and disconnection of a layer.

[0020]

This object is achieved by any one of the following constitutions (1) to (5). (1) A substrate having electrical insulation, an electrode layer having a pattern on the substrate, a dielectric layer covering at least a part of the electrode layer, and at least a light emitting layer and a transparent electrode layer on the dielectric layer And an EL element having a multilayer structure of a dielectric layer formed by a thick film and a solution coating baking method, wherein the EL layer has a buffer layer on at least the electrode layer. (2) The EL device according to (1), wherein the buffer layer is a high dielectric constant composition film formed by a sputtering method. (3) The EL device according to the above (1) or (2), wherein the high dielectric constant composition film has a perovskite structure dielectric composition and a relative dielectric constant of 100 or more. (4) The EL element according to any one of the above (1) to (3), wherein the buffer layer is disposed at least between the electrode layer and the dielectric layer formed by a solution coating and firing method. (5) The EL device according to any one of (1) to (4), wherein the buffer layer has a thickness of 10 nm or more.

[0021]

When a dielectric layer having a high dielectric constant is formed by a solution coating firing method for planarizing a surface, a solution coating firing dielectric layer (hereinafter referred to as a flattening layer) is used to flatten the entire surface of the thick ceramic dielectric layer. Must be larger than the ceramic dielectric. At this time, the lower electrode 12 shown in FIG.
The flattening layer 15 is formed directly on a part of the electrode lead-out portion for drawing the same from the thick dielectric layer.

The EL element shown in FIG. 10 has, for example, a lower electrode layer 12 formed in a predetermined pattern on a substrate 11 having electrical insulation, and a thick film dielectric layer 14 formed thereon.
And a dielectric layer 15 formed thereon by a solution coating method to form a multilayer dielectric layer.

The thin-film insulator layer 16, the light-emitting layer 17, and the thin-film insulator layer 1
8, the transparent electrode layer 19 is laminated, and the lower electrode layer 12
The upper transparent electrode layer 19 is formed in a stripe shape in a direction orthogonal to each other.

On the lower electrode, particularly when a flattening layer having a thickness of more than 0.5 μm is baked, high-density cracks 21 are likely to occur due to the following reasons.
Of the flattening layer due to the separation, generation of particles due to the separation 21, and separation of the electrode at the same time as the flattening layer.
Occurs frequently.

Such generation of particles due to the cracks 21, defects due to separation of the lower electrode layer, and disconnections 21
This leads to formation of pinholes in the light emitting layer by particles, disconnection of electrodes, and reduction in reliability, which is a fatal defect for EL elements.

The present inventors have found that the occurrence of such cracks and peeling commonly occurs in various kinds of precursor solutions for flattening layers, and analyzed the cause thereof. This is a problem in the firing process common to the methods, and the following estimation was made regarding the cause.

The precursor solution used in the solution coating and baking method comprises a metal organic compound or a metal alkoxide of the metal element constituting the dielectric layer and a complex of the metal source element and the organic substance in the solution, and further a volatile solvent. Be composed.

In the film forming method of the solution coating and firing method, a precursor layer is formed on a substrate by applying the precursor solution to a substrate by a method such as spin coating, dip coating, or spray coating. By firing this precursor layer, the organic components in the precursor are removed, an ultrafine oxide layer is formed by bonding of a metal element and oxygen, and the oxide layer is fired to form a dielectric layer. Is done.

FIG. 11 shows a change in the film thickness in the firing step. In the figure, the change in the relative film thickness in the firing step is shown, with the film thickness immediately after the application being set to 1. In this firing step, the following phenomenon occurs. First, at a relatively low temperature (up to 200 ° C.), the solvent component in the precursor volatilizes to a temperature corresponding to its boiling point, and the thickness of the applied precursor layer is greatly reduced. At this point, the film thickness is still considerably larger than the final film thickness, and since a large number of organic substances are present in the film, the film is mechanically soft and hardly cracks.

When the temperature further rises (up to 400 ° C.), the organic component is gradually volatilized by decomposition or the like from the complex of the metal source element and the organic substance (in the solution), and the film thickness further decreases and the film becomes thinner. The film becomes mechanically brittle, and a large tensile stress occurs due to the volume shrinkage of the film. At this point, the largest crack is likely to occur.

After this stage, the organic components are almost completely eliminated from the film, and when the crystalline dielectric film is formed by sintering of the oxide of the remaining metal element, mass transfer accompanying sintering occurs again in the previous stage. At the same time, the stress associated with sintering is generated. At this point, cracks are not so large.

It is presumed that the dielectric layer formed by the solution coating and baking method is usually formed in such a process. Naturally, the composition of the precursor solution and the coating and baking are set so that cracks do not occur in such a baking process. The conditions are set, but even if optimized as described above, the cracks occur very frequently on the metal electrode layer.

The reason for this is that in the above-described firing process,
The metal electrode layer has a different coefficient of thermal expansion from that of the substrate, and usually this coefficient of thermal expansion is larger than the coefficient of thermal expansion of the substrate, so that compressive stress is generated in the electrode layer, and minute hillocks are formed in the electrode. In addition, since the melting point of the metal constituting the electrode is not sufficiently high, a recrystallization phenomenon of the metal electrode occurs. For this reason, it is considered that the cause is that an excessive stress is locally applied to the solution-applied fired dielectric layer as compared with a normal ceramic or glass substrate.

As a result of estimating the cause of the cracks and studying as described above, the present inventors provided a buffer layer between the dielectric layer and the metal electrode layer, and mechanically moved the surface of the metal electrode layer. It has been found that the occurrence of cracks can be suppressed by providing a clamping effect.

[0035]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An EL device according to the present invention comprises a substrate having electrical insulation, an electrode layer having a pattern on the substrate, a dielectric layer covering at least a part of the electrode layer, and a dielectric layer. An EL element having at least a light emitting layer and a transparent electrode layer laminated on a body layer, wherein the dielectric layer has a multilayer structure of a thick film and a dielectric layer formed by a solution coating baking method, wherein at least the electrode layer Has a buffer layer.

As described above, by disposing the buffer layer on the electrode layer, cracking and peeling of the dielectric layer formed by the solution coating and baking method formed thereon can be prevented, and further, peeling of the lower electrode layer can be prevented. And disconnection can be prevented.

FIG. 1 shows the basic structure of the EL device of the present invention. The EL element according to the present invention includes, for example, a lower electrode layer 2 formed in a predetermined pattern on a substrate 1 having electrical insulation.
And a thick dielectric layer 4 over the buffer layer 3
And a dielectric layer 5 formed thereon by a solution coating method to form a multilayer dielectric layer.

On the multilayer dielectric layers 4 and 5, a thin-film insulator layer 6, a light-emitting layer 7, a thin-film insulator layer 8, and a transparent electrode layer 9 are laminated. Note that the thin film insulator layers 6 and 8 may be omitted. The lower electrode layer 2 and the upper transparent electrode layer 9 are formed in stripes in directions orthogonal to each other. Then, any lower electrode layer 2 and upper transparent electrode layer 9
Are selected, and a voltage is selectively applied from the AC power supply / pulse power supply 10 to the light emitting layer at the orthogonal portion of both electrodes, whereby light emission of a specific pixel can be obtained.

FIG. 2 shows another example of the configuration of the EL device of the present invention. In this example, the buffer layer 3 is formed on the thick film dielectric layer 4 so as to surround it. I have. Other components are the same as those in FIG. 1, and the same components are denoted by the same reference numerals and description thereof will be omitted. That is, the buffer layer 3 may be formed at any position as long as it is interposed between the lower electrode 2 and the dielectric layer 5 formed by the solution coating method.

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.

As a specific material, alumina (Al ₂
O ₃ ), quartz glass (SiO ₂ ), magnesia (Mg
O), forsterite (2MgO · SiO _2), steatite (MgO · SiO _2), mullite (3Al ₂ O ₃
2SiO ₂ ), beryllia (BeO), zirconia (Z
rO ₂ ), a ceramic substrate such as aluminum nitride (AlN), silicon nitride (SiN), silicon carbide (SiC), crystallized glass, or high heat-resistant glass.
Further, a metal substrate or the like on which an enamel treatment has been performed can also be used.

When the display device is a simple matrix type, the lower electrode layer is formed to have a plurality of stripe-shaped patterns. Further, the line width is the width of one pixel, and the space between the lines is a non-light emitting region. Therefore, it is preferable to minimize the space between the lines. Specifically, for example, the line width is 200 to 500 μm and the space 20
About 50 μm is required.

As a material of the lower electrode layer, a material which has high conductivity, is not damaged during the formation of the dielectric layer, and has low reactivity with the dielectric layer and the light emitting layer is preferable. Such lower electrode layer materials include Au, Pt, Pd,
Noble metals such as Ir and Ag, Au-Pd, Au-Pt and A
Noble metal alloys such as g-Pd and Ag-Pt, and Ag-Pd-
An electrode material containing a noble metal such as Cu as a main component and a nonmetal element added thereto is preferable because oxidation resistance to an oxidizing atmosphere during firing of the dielectric layer can be easily obtained. In addition, ITO or SnO ₂
(Nesa film), an oxide conductive material such as ZnO-Al may be used, and further, a base metal such as Ni or Cu may be used to oxidize the partial pressure of oxygen when firing the dielectric layer. It can also be used by setting it to a range not to be performed.

As a method for forming the lower electrode layer, a known technique such as a sputtering method, an evaporation method, and a plating method may be used.

In particular, the buffer layer of the present invention can be used as an electrode that easily exhibits a peeling-preventing effect.
old resinate, bright gold). The material referred to as gold solution or water gold is a terpene-based solvent containing gold in the form of an organometallic compound, usually about 4 to 25%, and is a brown viscous liquid. By using this gold solution, 50 to 50
An extremely thin and dense gold film of 0 nm can be obtained.

Since this gold solution is soluble in terpene and can be adjusted in viscosity freely, an electrode pattern can be formed by various coating and printing methods such as spraying and screen printing.

After the applied gold solution is dried,
A heat treatment at about 850 ° C. forms a gold wiring pattern.

The thick dielectric layer needs to have a high dielectric constant and a high withstand voltage, and further needs to be a material that can be fired at a low temperature in consideration of the heat resistance of the substrate.

Here, the thick film dielectric layer is a ceramic layer formed by firing a powdery insulating material by a so-called thick film method. This thick-film dielectric layer is formed, for example, by printing and firing an insulating paste made by mixing a binder and a solvent with a powdered insulating 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 insulator paste to form a film, and the green sheet may be formed by lamination.

The conditions for the binder removal treatment performed before firing are as follows:
It may be a normal one.

The atmosphere at the time of firing may be appropriately determined according to the type of the conductive material in the electrode layer paste. When firing in an oxidizing atmosphere, normal firing in air may be performed.

The holding temperature at the time of firing may be appropriately determined according to the type of the insulator layer, and is usually 700 to 1200 ° C.
Degree, preferably 1000 ° C. or less. Further, the temperature holding time during firing is 0.05 to 5 hours, particularly 0.1 to 3 hours.
Time is preferred.

Further, an annealing treatment may be performed if necessary.

Here, when the relative permittivity of the thick dielectric layer and the light emitting layer is e1 and e2, the film thickness is d1 and d2, and the voltage Vo is applied between the upper electrode layer and the lower electrode layer, the light emitting layer Is given by the following equation.

V2 / Vo = (e1 × d2) / (e1 × d2 + e2 × d1)-(1) Assuming that the relative permittivity of the light emitting layer is e2 = 10 and the film thickness is d2 = 1 μm. V2 / Vo = e1 / (e1 + 10 × d1) ------- (2)

The effective voltage applied to the light emitting layer is at least 50% or more of the applied voltage, preferably 80% or more, and more preferably 90% or more.

In the case of 50% or more, e1 ≧ 10 × d1 (3) In the case of 80% or more, e1 ≧ 40 × d1 (4) 90% or more In the case of, e1 ≧ 90 × d1 -------- (5)

That is, the relative dielectric constant of the dielectric layer must be at least 10 times, preferably at least 40 times, more preferably at least 90 times the film thickness when the unit is expressed in μm.

The thickness of the thick film dielectric is required to be large in order to eliminate pinholes formed by steps of the electrodes and dusts in the manufacturing process, etc., and is at least 10 μm or more, preferably 20 μm or more, more preferably 30 μm or more is required.

For example, if the thickness of the dielectric layer is 20 μm, its relative dielectric constant needs to be 200 to 800 to 1800 or more. If the thickness of the dielectric layer is 30 μm, its relative dielectric constant is 300 μm. ~ 1200 to 2700 are required.

Various materials can be considered as such a high-dielectric-constant thick-film material. However, considering the heat resistance of the substrate material, a high-dielectric-constant ceramic composition that can be formed at a low temperature is desirable.

For example, BaTiO ₃ , (Ba _x Ca _1-x ) T
iO ₃ , (Ba _x Sr _1-x ) TiO ₃ , PbTiO ₃ , P
Dielectric or ferroelectric material having a perovskite structure such as b (Zr _x Ti _1-x ) ₃ or Pb (Mg _1/3 Ni _2/3 ) O ₃
And the like, a bismuth layered compound represented by Bi ₄ Ti ₃ O ₁₂ and SrBi ₂ Ta ₂ O ₉ , (Sr _x Ba _{1 -x} ) Nb ₂
Tungsten bronze type ferroelectric materials typified by O ₆ , PbNb ₂ O _{6 and the} like are preferable because of their high dielectric constant and easy firing.

A dielectric material containing lead in its composition
Means that the melting point of lead oxide is as low as 888 ° C, and that lead oxide and other
Oxide-based materials such as SiO_Two And CuO, Bi_TwoO_Three ,
Fe_TwoO _Three 700 ℃ to 800 ℃ low temperature
Is easy to bake at low temperature because the liquid phase is formed, and
It is preferable because a high dielectric constant is easily obtained. For example, Pb (Zr_x
Ti_1-x)_ThreeOr a perovskite structure dielectric material such as Pb
(Mg_1/3Ni_2/3) O_ThreeCompound perovska represented by
Itraxer type ferroelectric material, PbNbO₆Etc.
Tungsten bronze-type ferroelectric materials represented
Can be These are ordinary ceramics such as alumina ceramics.
800-900 ° C, which is the upper temperature limit of Lamix substrate
Easily induces a dielectric constant of 1,000 to 10,000 at the firing temperature of
An electric body can be formed.

Since the purpose of the high dielectric constant dielectric layer laminated on the thick dielectric layer is to improve the surface flatness of the thick dielectric layer, it is necessary to use a solution coating baking method.

The solution coating baking method includes the sol-gel method and the MOD method.
It refers to a method of forming a dielectric layer by applying a precursor solution of a dielectric material to a substrate, such as a method, and baking.

The sol-gel method is generally a method in which a predetermined amount of water is added to a metal alkoxide dissolved in a solvent, and a precursor solution of a sol having MOM bonds formed by hydrolysis and polycondensation is applied to a substrate. And baking to form a film. Also, MOD (Metallo-Organic Decom
The position) method is a method in which a metal salt of a carboxylic acid having an MO bond or the like is dissolved in an organic solvent to form a precursor solution, which is applied to a substrate and baked to form a film. Here, the precursor solution refers to a solution containing an intermediate compound generated by dissolving a raw material compound in a solvent in a film forming method such as a sol-gel method or a MOD method.

The sol-gel method and the MOD method are not completely separate methods, but are generally used in combination with each other. For example, when forming a PZT film, it is common to adjust the solution using lead acetate as a Pb source and alkoxides as Ti and Zr sources. In addition, the sol-gel method and the MOD method are sometimes collectively referred to as a sol-gel method, but in any case, a precursor solution is applied to a substrate and a film is formed by baking to form a film. Then, a solution coating baking method is used. Further, even a solution obtained by mixing a submicron-sized dielectric particle and a precursor solution of the dielectric is included in the precursor solution of the dielectric of the present invention, and the solution may be applied to the substrate and fired. It is included in the solution coating and baking method of the present invention.

In the case of the solution coating and firing method, the elements constituting the dielectric are uniformly mixed in the order of sub-μm or less in both the sol-gel method and the MOD method. Compared with a method using ceramic powder sintering, it is possible to synthesize a dense dielectric at an extremely low temperature.

The main purpose of using the solution coating and baking method is that the dielectric layer formed by this method is formed through a step of applying and baking a precursor solution. Since a thick layer and a thin layer are formed on the protrusions, the step on the substrate surface is flattened, and the surface flatness of the thick ceramic dielectric layer of the EL element is remarkably improved. The uniformity of the thin film light emitting layer can be greatly improved.

Therefore, the thickness of the dielectric layer formed by the solution coating and baking method is desirably 0.5 μm or more, preferably 1 μm or more, more preferably 2 μm or more in order to sufficiently flatten the unevenness on the surface of the thick film. It is.

Here, the effect of the lamination of the dielectric layers by the solution coating and firing method on the relative dielectric constant of the entire dielectric layer will be described. The relative dielectric constants of the thick dielectric layer and the high dielectric constant dielectric layer formed by the solution coating baking method are e3 and e4, respectively.
When the total thickness of each layer is d3 and d4,
The effective relative permittivity e5 of the entire stacked dielectric layer is expressed by the following equation. (However, here, the film thickness of the entire laminated dielectric layer is d3
(Convert to dielectric constant as it does not change)

E5 = e3 × 1 / [1+ (e3 / e4) × (d4 / d3)] --- (6) By transforming this equation, e4 / d4 = e3 × e5 / (d3 × (e3-e5)) ------- (7)

From the above discussion, the effective relative dielectric constant of the entire laminated dielectric layer formed by the addition of the high dielectric constant dielectric layer formed by the solution coating and baking method was determined by setting the thickness of the thick film layer to 30 μm.
In this case, it is preferably 1200 to 2700 or more. Therefore, for example, when an attempt is made to obtain an effective dielectric constant of 2700 using a thick film having a relative dielectric constant of 4000, the ratio between the relative dielectric constant and the film thickness of the dielectric layer formed by the solution coating and firing method is 27.
7 or more, and the dielectric constant of the thick dielectric layer is 3000
If so, the ratio is 900.

As described above, the thickness of the dielectric layer formed by the solution coating baking method is at least 0.5 μm or more.
It is preferably at least 1 μm, more preferably at least 2 μm. Therefore, it is desirable that the relative dielectric constant is as high as possible, and is at least 250 or more, preferably 500 or more.

As described above, the high dielectric constant layer formed by the solution coating and baking method needs to have a large thickness and a high dielectric constant. As such a high dielectric constant material, for example, BaTiO ₃ , (Ba _x Ca _1-x ) TiO ₃ , (Ba
_x Sr _1-x ) TiO ₃ , PbTiO ₃ , Pb (Zr _x Ti
_1-x ) A dielectric material having a perovskite structure such as ₃ or a ferroelectric material, a composite perovskite relaxer type ferroelectric material represented by Pb (Mg _1/3 Ni _2/3 ) O ₃ or the like;
Bismuth bismuth layered compound (Sr _x Ba _1-x ) Nb ₂ O ₆ typified by i ₄ Ti ₃ O ₁₂ and SrBi ₂ Ta ₂ O ₉ ;
Tungsten bronze type ferroelectric materials typified by PbNbO ₆ and the like are listed. Among them, BaT
A ferroelectric material having a perovskite structure, such as iO ₃ or PZT, is preferable because it has a high dielectric constant and can be easily formed at a relatively low temperature.

It is necessary that the buffer layer itself does not cause cracks on the metal electrode and has a sufficient mechanical clamping effect. Therefore, the buffer layer does not undergo excessive volume shrinkage during the formation of the buffer layer or during the baking process by the solution coating and baking method after the formation of the buffer layer, and is sufficiently harder than the metal electrode, and has an appropriate thickness. It is necessary to have.

As a method of forming such a buffer layer, the density of the buffer layer is sufficiently high at the time when the buffer layer is formed, and the volume shrinkage of the buffer layer during firing of the solution-coated firing layer after the formation of the buffer layer is small. A method that can exert a clamping effect of the electrode layer is preferable. That is, as a method for forming the buffer layer, a method in which a large volume shrinkage occurs in the process of forming an intended structure, such as the solution coating and baking method described above, is not preferable, and a dense film formation method without volume shrinkage is not preferable. Needed.

As a method for forming such a film, a method such as a vacuum evaporation method, a sputtering method, or a CVD method is used, and a film having a composition and a density close to the target composition is directly formed on a substrate without post-heat treatment or the like. A film formation method that can be formed is required.

Of these, the sputtering method is a particularly preferred method because a thin film having the same composition as the target composition can be easily formed. The sputtering method has a density of 95% or more in a crystallized thin film and a density of 80% or more in an amorphous thin film. A thin film can be easily formed.

Next, the effect of the dielectric constant of the buffer layer will be described.

Here, the relative permittivity of the dielectric layer and the buffer layer is e7 and e6, respectively, and the thickness of each layer is d
In the case of 7, d6, the effective relative permittivity e8 of the laminated dielectric layer and buffer layer is expressed by the following equation.

E8 = e6 × 1 / [1+ (e6 / e7) × (d7 / d6)] ------- (8)

The reduction of the effective relative permittivity of the dielectric layer / buffer layer composite layer due to the insertion of the buffer layer is caused by the relative permittivity between the dielectric layer and the light emitting layer and the effective voltage applied to the light emitting layer. In view of the relationship, it is necessary that the relative dielectric constant of the composite layer is at least 90% or more, preferably 95% or more of the dielectric layer alone. Therefore, from equation (8),

In the case of 90% or more, e6 / d6 ≦ 1/9 × e7 / d7 --- (9) In the case of 95% or more, e6 / d6 ≦ 1/19 × e7 / d7- ------ (10)

For example, assuming that the relative permittivity of the dielectric layer is 2700 and the film thickness is 30 μm, the ratio between the relative permittivity and the film thickness of the buffer layer is 810 or more, preferably 1710 or more.

Therefore, for example, when the thickness of the buffer layer is 0.1
If it is assumed to be μm, the relative permittivity must be 1 to 171 or more, and if it is assumed to be 0.01 μm, the relative permittivity is 8.1 to 1
7.1 or more is required.

The thickness of the buffer layer may be any value as long as the effect of suppressing the occurrence of cracks during the formation of the dielectric layer due to the interaction between the electrode layer and the dielectric layer can be obtained. It is expected that the effect will be more remarkable if it is larger. According to the experimental study of the present inventors, in the case of an oxide thin film formed by a sputtering method, the crack suppressing effect is sufficiently recognized from a film thickness of 10 nm or more, and the crack suppressing effect improves as the film thickness increases. However, it became clear that cracks on the electrode completely disappeared when the thickness was 100 nm or more.

Therefore, the required film thickness is at least 10 nm or more, preferably 100 nm or more. This effect is also observed up to a thickness of about 1 μm, but thicker thicknesses may cause overhangs. Therefore, the upper limit is preferably 1 μm or less, more preferably １ ／ or less of the electrode layer thickness.

Materials for the buffer layer include alumina (dielectric constant: 8), zirconia (dielectric constant: about 10), Ta ₂ O ₅
An insulating material such as (a relative dielectric constant of about 25) can be used. However, in view of the above-described relationship between the relative dielectric constant and the film thickness, the effect of suppressing cracks, and the reactivity with the dielectric layer, a high dielectric constant is preferable. Materials such as TiO ₂ (dielectric constant about 80),
Particularly preferably, a high dielectric constant material having a relative dielectric constant of 100 or more, for example, a pyrochlore type dielectric such as Pb ₂ (Zr _{1 -y} Ti _y ) ₂ O ₆ , Bi ₄ Ti ₃ O ₁₂ , SrBi ₂ Ta ₂ O ₉
Such as Bi layered compound type dielectrics, barium titanate (BaTiO ₃ ), strontium titanate (SrTiO ₃ ), calcium titanate (CaTi)
O ₃ ), lead titanate (PbTiO ₃ ), lead zirconate (P
bZrO ₃ ) and other perovskite-type high dielectric constant materials, their mixtures, and solid solution compositions ((Ba
_1-x Sr _x ) TiO ₃ , PZT, etc.) and perovskite-type relaxor oxides are preferred. Among these, BaT
Ferroelectric materials having a perovskite structure, such as iO ₃ and PZT, are preferred because they have a high relative dielectric constant and can be easily synthesized at a relatively low temperature. Such a material can easily make the relative dielectric constant suitable for the buffer layer 100 or more.

Further, by using a material having the same crystal structure as the dielectric layer formed by the solution coating and firing method, it is possible to easily avoid the reaction between the dielectric layer and the buffer layer, the formation of a different phase of the dielectric layer, and the like. it can. Further, if the composition is the same, it is possible to completely eliminate the decrease in the effective relative permittivity of the buffer layer / dielectric layer composite layer due to the use of the buffer layer, and to reduce the effective voltage value applied to the light emitting layer. Drops can be avoided.

As a result of detailed experiments by the present inventors, it was confirmed that the above effects were particularly effective under the following conditions.

First, a buffer layer is formed on the surface of the lower electrode in a portion where the dielectric layer and the lower electrode layer may be in direct contact with each other by the solution coating and baking method. This buffer layer prevents cracks in the solution-applied baked dielectric layer formed directly on the lower electrode, and peels off the dielectric layer,
The separation and the defect of the lower electrode layer accompanying the separation can be eliminated. This prevents the formation of pinholes in the light emitting layer due to the generation of particles, and prevents defects and disconnections in the lower electrode layer, whereby a high-quality and highly reliable EL element can be manufactured with a high yield. In particular, when manufacturing a high-definition display panel, the size of individual pixels is reduced, and the line width of the lower electrode is also reduced, thereby increasing the reliability of the lower electrode and the importance of preventing particles. In this case, the insertion of a buffer layer is particularly effective.

Second, the buffer layer is made of a high dielectric constant composition film formed by a sputtering method. Since a high-density buffer layer can be formed by using a high dielectric constant composition film formed by a sputtering method, a mechanical clamping effect of a metal electrode is generated from a very thin region having a thickness of 10 nm. Cracking of the dielectric first layer by the method can be suppressed. By using such a thin buffer layer and using a high dielectric constant composition, it is possible to minimize the decrease in the effective relative dielectric constant of the dielectric layer due to the interposition of the buffer layer. Become.

Third, the high dielectric constant composition film is made of a substance having a relative dielectric constant of 100 or more using a perovskite structure dielectric composition. By setting the relative dielectric constant to 100 or more, it is possible to minimize the effective decrease in the dielectric constant of the dielectric layer due to the interposition of the buffer layer.

The material for the light-emitting layer is not particularly limited, but known materials such as the above-mentioned Mn-doped ZnS can be used. Among them, 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 luminous efficiency decreases. Specifically, although it depends on the luminescent material, it is preferably 100 to 20.
It is about 00 nm.

As a method for forming the light emitting layer, a vapor phase deposition method can be used. As the vapor deposition method, a physical vapor deposition method such as a sputtering method or a vapor deposition method or a chemical vapor deposition method such as a CVD method is preferable. In addition, as described above, in particular, SrS:
When a Ce light emitting layer is formed, the substrate temperature during film formation is set to 50 in an H ₂ S atmosphere by electron beam evaporation.
When formed at a temperature of 0 ° C. to 600 ° C., a high-purity light-emitting layer can be obtained.

After the formation of the light emitting layer, a heat treatment is preferably performed. The heat treatment may be performed after the electrode layer, the dielectric layer, and the light-emitting layer are stacked from the substrate side, or the electrode layer, the dielectric layer, the light-emitting layer, the insulator layer, or the electrode layer is formed therefrom from the substrate side. After that, heat treatment (cap annealing) 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,
It is lower than the firing temperature of the dielectric layer. Processing time is 10-60
Preferably, it is 0 minutes. The atmosphere during heat treatment, the composition of the luminescent layer, the forming conditions air, may be selected from N _2, the He and Ar, and the like.

The thin-film insulator layer (6) and / or (8)
May be omitted as described above, but is preferably provided.

The function of the thin-film insulator layer is to adjust the electronic state at the interface between the light-emitting layer and the dielectric layer to stabilize and improve the electron injection into the light-emitting layer. The main purpose is to improve the positive-negative symmetry of the emission characteristics during AC driving by symmetrically configuring both sides of the light-emitting layer, and consider the function of maintaining the dielectric strength, which is the role of the light-emitting layer dielectric layer. Since it is not necessary to perform the process, the film thickness may be small.

This thin-film insulator layer has a resistivity of 10
^It is preferably at least ⁸ Ω · cm, particularly preferably about 10 ¹⁰ to 10 ¹⁸ Ω · cm. Further, it is preferable that the material has a relatively high relative dielectric constant, and the relative dielectric constant ε thereof is preferably ε =
3 or more. As a constituent material of this thin film insulator layer,
For example, silicon oxide (SiO ₂ ), silicon nitride (Si
N), tantalum oxide (Ta ₂ O ₅ ), yttrium oxide (Y ₂ O ₃ ), zirconia (ZrO ₂ ), silicon oxynitride (SiON), alumina (Al ₂ O ₃ ), and the like. As a method for forming the thin film insulator layer, a sputtering method, an evaporation method, or a CVD method can be used. The thickness of the thin-film insulator layer is preferably 10 to 1000 nm, particularly preferably 20 to 20 nm.
It is about 0 nm.

For the transparent electrode layer, an oxide conductive material such as ITO, SnO ₂ (Nesa film), ZnO—Al or the like having a thickness of 0.2 μm to 1 μm is used. As a method for forming the transparent electrode layer, a known technique such as a vapor deposition method other than the sputtering method may be used.

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 structure, and a plurality of light-emitting layers may be stacked in the film thickness direction. Alternatively, different types of light emitting layers (pixels) may be combined in a matrix and arranged in a plane.

As described above, the EL device of the present invention has extremely good smoothness of the surface of the dielectric layer on which the light emitting layer is laminated, high withstand voltage and no defects. Therefore, a high-performance, high-definition display having high luminance and high long-term reliability of luminance can be easily configured. Further, the manufacturing process is easy, and the manufacturing cost can be reduced.

[0104]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically shown below and described in more detail. On a 96% -purity alumina substrate, an Au thin film to which a trace amount of an additive was added was formed to a thickness of 1 μm as a sample 1 to 9 by a sputtering method.
And heat-treated for stabilization. The Au lower electrode layer was formed by photolithography to a width of 300 μm and a space of 30 μm.
It was patterned into a number of μm stripes.

Similarly, Heraus RP 2003 / 237-2 was prepared as samples 10 and 11 on an alumina substrate.
Using 2% resinate gold paste, film thickness after firing is 1μ
screen printing on the same pattern as above so that m
Drying was repeated. Thereafter, firing was performed at 850 ° C. for 20 minutes in an atmosphere in which sufficient air was supplied.

A dielectric ceramic thick film was further formed on the substrate on which the lower electrode was formed by a screen printing method. As a thick film paste, ESL 4210C
Using a thick film dielectric paste, screen printing and drying were repeated so that the film thickness after firing became 30 μm.

After the 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. The dielectric constant of this thick film alone was about 4000.

Next, BaTiO ₃ , SrTiO ₃ , Ti
Each thin film of O ₂ was formed on the substrate by a sputtering method, and used as each buffer layer.

As the conditions for forming the BaTiO ₃ thin film, a magnetron sputtering apparatus was used, BaTiO ₃ ceramic was used as a target, and a pressure of Ar gas was 3 Pa.
Film formation was performed under the conditions of a 56 MHz high frequency power density of 2 W / cm ² .

At this time, the film forming speed is about 5 nm / min.
Was obtained. The BaTiO ₃ formed at this time
The thin film is in an amorphous state, and has a film density of 80 to 90.
%Met. The relative dielectric constant of the sputtered film was about 20, and when this film was heat-treated at 700 ° C., a value of 500 was obtained. Further, it was confirmed by an X-ray diffraction method that the heat-treated BaTiO ₃ thin film had a perovskite crystal structure.

The conditions for forming the SrTiO ₃ thin film include Sr
The TiO ₃ ceramic as a target, the BaT
It was the same as the iO ₃ thin film. The film formation speed is about 4 nm / min, and the film thickness is 100 nm by adjusting the sputtering time.
Was obtained. The SrTiO ₃ formed at this time
The thin film is in an amorphous state, and has a film density of 80 to 90.
%Met. The relative permittivity of the sputtered film could not be measured due to the high conductivity of the film.
After heat treatment at 00 ° C., values of relative dielectric constant of 200 to 300 were obtained. Further, it was confirmed by an X-ray diffraction method that the heat-treated SrTiO ₃ thin film had a perovskite crystal structure. This film was heat-treated at a temperature of 600 ° C., but the same result was obtained even when the heat treatment was performed at a temperature of 500 to 700 ° C.

The conditions for forming the TiO ₂ thin film were as follows: a magnetron sputtering apparatus, a TiO ₂ ceramic as a target, an Ar gas pressure of 1 Pa, and 13.56 MHz.
Film formation was performed under the condition of a high frequency power density of 2 W / cm ² .

At this time, the film formation rate is about 2 nm / min.
Was obtained. BaTiO ₃ formed at this time
The thin film is in an amorphous state, and has a film density of 80 to 90.
%Met. The relative permittivity of the sputtered film could not be measured due to the high conductivity of the film.
After heat treatment at 00 ° C., a value of relative permittivity of 80 was obtained. This film was heat-treated at a temperature of 600 ° C.
The results were the same even when the heat treatment was performed at a temperature of 00 to 700 ° C.

A dielectric layer was formed on these substrates by using a solution coating baking method. As a method of forming the dielectric layer by the solution coating and baking method, a sol-gel solution of PZT prepared by the following method was prepared and used as a precursor solution of the solution coating and baking method. First, the operation of applying the precursor solution to the substrate on which the buffer layer was formed by spin coating and firing at 700 ° C. for 15 minutes was repeated a predetermined number of times.

The basic method for preparing a sol-gel solution is described in 8.4.
9 g of lead acetate trihydrate and 4.17 g of 1.3 propanediol were heated and stirred for about 2 hours to obtain a clear solution.
Separately, 3.70 g of a 70% by mass zirconium normal propoxide, 1-propanol solution;
58 g of acetylacetone was heated and stirred in a dry nitrogen atmosphere for 30 minutes, and added to 3.14 g of titanium diisopropoxide bisacetylacetonate 75% by mass.
A 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 produce a brown transparent solution. Add this solution to 13
By holding at 0 ° C. for several minutes to remove by-products,
A PZT precursor solution was prepared by further heating and stirring for 3 hours.

The viscosity of the PZT precursor solution was adjusted by diluting it with n-propanol. The thickness of the dielectric layer per single layer can be adjusted to about 0.1 layer by adjusting the spin coating conditions and the viscosity of the sol-gel solution.
7 μm. The above sol-gel solution was used as a PZT precursor solution, and application and baking by spin coating were repeated four times to form a PZT dielectric layer having a thickness of about 3 μm.

The dielectric constant of the laminated structure of the thick ceramic dielectric layer and the PZT layer formed by the solution coating and firing method is as follows.
Assuming that the total film thickness is unchanged at 30 μm, about 2
800.

The obtained substrate with a PZT dielectric layer (flattening layer) was evaluated for cracks, peeling, disconnection rate, and particles. The evaluation was made by visual observation except for the disconnection, and the presence or absence of the disconnection was determined by using an HP3456A digital meter, and the one from one end to the other end of one electrode pattern having a resistance of 1 MΩ or more was determined as a disconnection. Table 1 shows the results
Shown in

[0119]

[Table 1]

FIGS. 3 to 8 show the results when the first dielectric layer was formed by using the PZT sol-gel solution of the present embodiment and changing the thickness of the BaTiO ₃ buffer layer formed by sputtering. It is a SEM and an optical microscope photograph.

Here, FIG. 3: Sample 1 (SEM photograph:
Fig. 6: Sample 2 (SEM photograph: long side =
250 μm), FIG. 7 sample 3 (SEM photograph: long side = 250 μm)
m), FIG. 8 Sample 6 (SEM photograph: long side = 250 μm), FIG. 4: Sample 10 (optical micrograph: long side = 1000 μm),
Figure 3: Sample 11 (optical micrograph: long side = 1000μm)
It is.

As is clear from the figure, when there is no BaTiO ₃ buffer layer, high-density cracks are generated, particularly in an electrode sample using Au resinate. When the thickness of the BaTiO ₃ buffer layer is 10 nm or more, cracks are reduced equally, and when the thickness is 100 nm, no cracks occur.

As is clear from Table 1, BaTi
When no O ₃ buffer layer was provided, disconnection of the lower electrode occurred, and further generation of particles was confirmed.

On the other hand, the BaTiO ₃ buffer layer
When the thickness was 0 nm or more, peeling of the lower electrode was not recognized, and when the film thickness was 100 nm, generation of cracks and particles was not recognized at all.

The effective dielectric constant of the buffer layer and the dielectric layer together showed almost no change even in the presence of the buffer layer. This is because even if the BaTiO ₃ film of the buffer layer is amorphous and has a low dielectric constant at the film forming point, the composition is a high dielectric constant dielectric composition, so the upper dielectric layer is formed by a solution coating baking method. This is thought to be due to crystallization by a high temperature treatment at the time and a high dielectric constant.

Also, when the SrTiO ₃ buffer layer and the TiO ₂ buffer layer having the same thickness were used, no peeling of the lower electrode occurred and no generation of particles was observed.

Next, the samples 1, 2, 3, 6,
Using the substrates with the dielectric layers of 8, 9, 10 and 11, E
An L element was produced.

The luminescent layer was heated to 200 ° C.
A ZnS luminous body thin film was formed to a thickness of 0.8 μm by a vacuum vapor deposition method using a ZnS vapor deposition source doped with, and then heat-treated at 600 ° C. for 10 minutes in a vacuum.

Next, an EL element was formed by sequentially forming a Si ₃ N ₄ thin film as an insulator layer and an ITO thin film as an upper electrode layer by a sputtering method. At that time, the ITO thin film of the upper electrode layer was patterned in a stripe shape of 1 mm width by using a metal mask at the time of film formation. The emission characteristics were measured by extracting electrodes from the lower electrode and the upper transparent electrode of the obtained device structure and applying an electric field until the emission luminance was saturated with a 1 kHz pulse width of 50 μs. In addition, a predetermined number of each EL element was prepared and evaluated.

As a result, in all samples, saturation luminance of 7000 cd / m ² was obtained. Samples 6 and 8 had an emission threshold of 160 V, whereas sample 9 had an emission threshold of 160 V. It rose to 170V. This is sample 9
The dielectric constant of the TiO ₂ film used for the sample was BaT of samples 6 and 8.
This is probably because iO ₃ and SrTiO ₃ are small.

In Samples 1, 2, and 10, non-light-emitting pixels were generated due to disconnection of the lower electrode layer. In Samples 1, 2, 3, and 10, abnormal light-emitting points and non-light-emitting points occurred in the light-emitting portions (pixels). This is considered to be due to the formation of a pinhole or a thin portion of the light emitting layer in the light emitting layer due to the generation of particles.

[0132]

As described above, according to the present invention, in the EL device in which the surface flatness of the thick-film ceramic dielectric layer is secured by the sol-gel dielectric layer, the lower part generated by adding the sol-gel dielectric layer is formed. It is possible to provide a highly reliable EL element free from defects by preventing peeling or disconnection of the electrode layer.

[Brief description of the drawings]

FIG. 1 is a partial schematic cross-sectional view showing a basic configuration of an EL element of the present invention.

FIG. 2 is a partial schematic cross-sectional view showing another basic configuration of the EL element of the present invention.

FIG. 3 is a photograph in place of a drawing in which the surface of a substrate with a PZT dielectric layer (planarization layer) of an example is photographed.

FIG. 4 is a photograph in place of a drawing in which the surface of a substrate with a PZT dielectric layer (planarization layer) of an example is photographed.

FIG. 5 is a photograph in place of a drawing in which the surface of a substrate with a PZT dielectric layer (planarization layer) of an example is photographed.

FIG. 6 is a drawing substitute photograph of the surface of a substrate with a PZT dielectric layer (planarization layer) of an example.

FIG. 7 is a photograph in place of a drawing in which the surface of a substrate with a PZT dielectric layer (planarization layer) of an example is photographed.

FIG. 8 is a drawing-substitute photograph of the surface of a substrate with a PZT dielectric layer (planarization layer) of an example.

FIG. 9 is a partial schematic cross-sectional view showing a basic configuration of a conventional thin film EL element.

FIG. 10 is a partial schematic cross-sectional view showing a basic configuration of a conventional thick film EL element.

FIG. 11 is a graph showing a change in film thickness when a conventional dielectric layer is fired.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Lower electrode 3 Buffer layer 4 Thick film dielectric layer 5 Dielectric layer 6 Thin film insulator layer 7 Light emitting layer 8 Thin film insulator layer 9 Transparent electrode layer 10 AC power supply 11 Substrate 12 Lower electrode 14 Thick film dielectric layer 15 Dielectric layer 16 Thin film insulator layer 17 Light emitting layer 18 Thin film insulator layer 19 Transparent electrode layer 20 AC power supply

Continued on the front page (72) Inventor Katsuto Nagano 1-13-1 Nihonbashi, Chuo-ku, Tokyo FDT term in TDK Corporation (reference) 3K007 AB11 AB18 BA06 CA02 CB01 DA05 DB02 DC02 EA02 EC01 EC03 EC04 FA01

Claims (5)

[Claims] 1. An electrically insulating substrate, an electrode layer having a pattern on the substrate, a dielectric layer covering at least a part of the electrode layer, and at least a light emitting layer and a transparent layer on the dielectric layer. An EL device having an electrode layer laminated thereon, wherein the dielectric layer has a multilayer structure of a thick film and a dielectric layer formed by a solution coating baking method, wherein the EL device has at least a buffer layer on the electrode layer. 2. The EL according to claim 1, wherein the buffer layer is a high dielectric constant composition film formed by a sputtering method.
element. 3. The EL device according to claim 1, wherein said high dielectric constant composition film has a perovskite structure dielectric composition and a relative dielectric constant of 100 or more. 4. The EL device according to claim 1, wherein said buffer layer is disposed between at least an electrode layer and a dielectric layer formed by a solution coating and baking method. 5. The EL device according to claim 1, wherein said buffer layer has a thickness of 10 nm or more.