JP2003347062A - Manufacturing method for el element and el element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for an EL element having high manufacturing stability and no EL light emission unevenness when driving the element and the EL element, in the EL element securing surface flatness of a thick film ceramics dielectric layer by a sol-gel dielectric layer. <P>SOLUTION: In this manufacturing method for the EL element, a substrate 1 having electric insulation, a first electrode layer 2 having a pattern on the substrate 1, dielectric layer 4 and 5 coating at least part of the electrode layer 2, and at least a light emitting layer 7 and a second electrode layer 9 on the dielectric layers 4 and 5 are sequentially laminated, and the dielectric layer 4 has a multilayered structure of a first dielectric layer 4 of a thick film and a second dielectric layer 5 formed by a solution coating and baking method. A buffer layer 3 is arranged between the substrate 1 formed with the electrode layer 2 and the first dielectric layer 4. Subsequently, the manufacturing method for the EL element constituted to bake the first dielectric layer 4 is obtained, and the EL element is obtained by this method. <P>COPYRIGHT: (C)2004,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an EL device having at least a structure in which a substrate having electrical insulation, an electrode layer having a pattern on the substrate, a dielectric layer, a light emitting layer and a transparent electrode layer are laminated on the electrode layer. The present invention relates to a manufacturing method and an EL device.

[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. 16 shows a typical example of a conventional EL device.
The structure of a heavy insulation type thin film EL device is shown. 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 , Al 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.

[0008] Also, the 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.

FIG. 17 shows a basic structure of a conventional EL device having such a sol-gel flattening layer. The EL element in the illustrated example is composed of, for example, a lower electrode layer 12 formed in a predetermined pattern on a substrate 11 having electric insulation, a thick dielectric layer (first dielectric layer) 14 thereon, Further, a second dielectric layer 15 formed by a sol-gel method is laminated thereon to form a multilayer dielectric layer.

The thin-film insulator layer 16, the light-emitting layer 17, the thin-film insulator layer 1
8. The transparent electrode layer 19 is laminated. Note that the thin film insulator layers 16 and 18 may be omitted. The lower electrode layer 12 and the upper transparent electrode layer 19 are formed in stripes in directions orthogonal to each other. Then, an arbitrary lower electrode layer 12 and an upper transparent electrode layer 19 are respectively selected, and light is emitted from a specific pixel by selectively applying a voltage from an AC power supply / pulse power supply 20 to a light emitting layer at an orthogonal portion of both electrodes. Obtainable.

However, the above-mentioned thick-film dielectric layer is porous in nature, and large irregularities larger than the above-described surface roughness may be locally generated. -There was a problem that it was difficult to completely flatten the gel layer.

That is, when such a thick film having local unevenness in unevenness is flattened by baking PZT or the like formed by the sol-gel method, a large variation occurs in the roughness of the surface after the flattening. This variation in the surface roughness results in uneven light emission at low luminance during EL light emission, and when it is significant, cracks may occur in the flattening layer. Cracks cause abnormal light emission called bright spots, and in any case cause uneven light emission.

[0021]

SUMMARY OF THE INVENTION An object of the present invention is to provide an EL device in which the surface flatness of a thick ceramic dielectric layer is ensured by a sol-gel dielectric layer. An object of the present invention is to provide a method for manufacturing an EL element without unevenness and an EL element.

[0022]

This object is achieved by any one of the following constitutions (1) to (5). (1) A substrate having electrical insulation, a first 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 on the dielectric layer An EL having a multilayer structure of a first dielectric layer in which a second electrode layer is sequentially stacked, the dielectric layer being a thick film, and a second dielectric layer formed by a solution coating and firing method.
A method for manufacturing an element, comprising: disposing a buffer layer on at least an electrode layer between a substrate on which the electrode layer is formed and a first dielectric layer, and thereafter firing the first dielectric layer. Manufacturing method. (2) The method for manufacturing an EL element according to the above (1), wherein the buffer layer is formed of a material which is solid-dissolved and integrated with the first dielectric layer material by firing. (3) The method for manufacturing an EL device according to the above (1) or (2), wherein the buffer layer is formed of tantalum oxide or barium titanate. (4) An EL device manufactured by any one of the above (1) to (3). (5) The EL device according to (4), wherein the buffer layer and the first dielectric layer are formed into a solid solution and integrated.

[0023]

The present inventors have studied the cause of the occurrence of irregularities in the thick film dielectric layer and found that a high dielectric constant thick film dielectric layer for sintering powder such as PMN-PT on the internal electrode is formed. Is that the sintering behavior of the thick-film dielectric layer differs between the internal electrode pattern and the substrate ceramic in the space where no internal electrode exists, resulting in a difference in sintering density, It was found that unevenness easily occurred in the sintering density on the thick dielectric layer on the electrode. Further, as a result of such a phenomenon, especially in the thick film on the electrode pattern and near the boundary (electrode end) between the non-electrode portion (space portion) and the thick film on the other electrodes, such a phenomenon is particularly caused. It was found that various sintering density irregularities occurred. For this reason, large irregularities occur on the surface of the thick-film dielectric layer after firing.

When PZT or the like prepared by the sol-gel method is applied to the surface, baked, and flattened, large variations occur in the roughness of the PZT surface after the flattening process. This variation in surface roughness results in light emission unevenness at low luminance during EL light emission. Furthermore, if the variation is remarkable, PZT
It was found that cracks occurred in the light-emitting elements, which caused abnormal light emission called luminescent spots, and in any case, caused uneven light emission.

As a means for preventing the occurrence of such unevenness, a thin film buffer layer is interposed between an internal electrode and a porous sintered body such as PMN-PT, so that PMN
-A high dielectric constant ceramic insulating layer for sintering powders such as PT can be fired at a uniform density, and surface irregularities can be reduced. As a result, when PZT or the like is baked and flattened, by reducing the thickness unevenness of PZT, EL is reduced.
Light emission unevenness can be prevented. In addition, generation of cracks can be suppressed.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION
An electrically insulating substrate, a first 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 second layer on the dielectric layer. A method for manufacturing an EL device having a multilayer structure of a first dielectric layer in which electrode layers are sequentially stacked, and wherein the dielectric layer is a thick film, and a second dielectric layer formed by a solution coating baking method. And disposing a buffer layer at least on the electrode layer between the substrate on which the electrode layer is formed and the first dielectric layer, and thereafter firing the first dielectric layer.

As described above, by arranging the buffer layer at least on the electrode layer, forming the thick-film dielectric layer thereon, and firing it, the sintering density of the thick-film dielectric layer formed thereon is increased. Can be prevented, and the surface can be prevented from being uneven.

The buffer layer is formed for the purpose of correcting uneven sintering density of the thick film dielectric layer formed thereon. For this reason, the buffer layer is preferably made of the same oxide material as the dielectric layer, and is particularly preferably a material that forms a solid solution with and is integrated with the constituent material of the thick-film dielectric layer.

The buffer layer corrects the difference in sintering density between the thick film dielectric layer on the patterned electrode and the thick film dielectric layer on the substrate other than the electrode formation region.
It must be interposed at least between the electrode and the thick dielectric layer in the display area. At this time, the electrode layer,
A so-called solid buffer layer may be formed so as to cover the entire space where the electrode layer is not formed. Also,
In consideration of the fact that the thick film dielectric layer and the thick film dielectric layer are integrated after firing, it is not necessary to form the thick film dielectric layer so as to protrude from the formation region. However, in order to confirm the trace of the buffer layer, it is formed in a region not absorbed by the thick film dielectric layer,
You may make it possible to confirm the remaining buffer layer.

The thickness of the buffer layer may be a thickness capable of correcting the non-uniformity of the sintering density of the thick dielectric layer. In this case, it is expected that the effect becomes more remarkable as the film thickness increases. According to experimental studies by the present inventors, in the case of an oxide thin film formed by a sputtering method, the effect is sufficiently recognized from a film thickness of 10 nm or more, and the effect is improved as the film thickness increases, and the effect is improved to 30 nm or more. It became clear that the nonuniformity of the density of the thick film dielectric layer completely disappeared.

Therefore, the required film thickness is at least 10 nm or more, preferably 30 nm or more. In addition, the buffer layer forms a solid solution with the constituent material of the thick film dielectric layer by firing,
For integration, it is substantially absorbed by the thick dielectric layer.
However, if it is too thick, it will remain without being absorbed by the thick dielectric layer, and if a low dielectric constant material is used, the element characteristics will be affected. Therefore, especially when a low dielectric constant material that can be relatively easily formed is used, the upper limit is preferably 0.1 μm or less, more preferably 0.8 μm or less.

As a material of the buffer layer, a ceramic material such as a metal oxide in a broad sense is preferable, and a material which forms a solid solution with a thick-film dielectric material is particularly preferable.

Specifically, the difference depends on the thick dielectric layer used.
But tantalum oxide (TaO)_x , Typically Ta_Two O
_Five ), Barium titanate (BaTiO)_Three )
Perovskite oxide (ABO_Three : A = Ba, Sr,
At least one element selected from Ca, B = Ti,
Zr, at least one element selected from Hf), acid
Titanium chloride (TiO_Two ), Lead titanate (PbTiO)_Three ),
Yttrium oxide (Y _TwoO_Three ), Niobium oxide (Nb_TwoO
_Five ), Zirconium oxide (ZrO)_Two ), PZT etc. are preferred
New Among these, especially tantalum oxide, titanic acid
Barium and titanium oxide are preferred.

As such a film forming method, a method such as a vacuum evaporation method, a sputtering method, a CVD method, and a sol-gel method may be used.

Next, the manufacturing method of the present invention will be described with reference to the drawings. First, as shown in FIG. 3, a lower electrode 2 is formed on a substrate 1 in a predetermined pattern. Lower electrode 2
Can be formed by a sputtering method, an evaporation method, a coating method, or the like as described later. The pattern may be formed at the time of forming the electrode layer such as mask evaporation, or may be formed by a known patterning method such as photoetching after forming the electrode layer.

Next, as shown in FIG. 4, a buffer layer 3 is formed on the substrate 1 on which the electrode pattern 2 has been formed. The buffer layer can be formed by a sputtering method, an evaporation method, or the like as described above.

Further, as shown in FIG.
A thick film dielectric layer 4 is formed on the substrate 1 on which is formed.
The thick film dielectric layer 4 can be formed by a screen printing method or a known thick film method of laminating green sheets. And the obtained thick film dielectric layer precursor (green)
By firing (heat-treating) the substrate 1 on which is formed at a predetermined temperature, the sintered body 4 in which the buffer layer 3 is absorbed by the thick film dielectric 4 and integrated as shown in FIG. 6 is obtained. The obtained sintered body has a uniform sintering density both on the electrode and on the substrate on which the electrode is not formed, and there is no large unevenness on the surface. At this time, it was formed in a region other than the thick-film dielectric layer 4 formation region (more specifically, it was formed so as to protrude from the thick-film dielectric layer 4 formation region).
The buffer layer 3 remains without being absorbed by the thick film dielectric layer 4.

Further, a second dielectric layer, a thin film insulating layer, a light emitting layer, a thin film insulating layer, and an upper electrode formed on the thick film dielectric layer (first dielectric layer) 4 by a solution coating method. (Transparent electrodes) and the like are sequentially formed to obtain an EL element.

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.
A thick dielectric layer (first dielectric layer) 4 on which a buffer layer 3 is absorbed, and a second dielectric layer 5 formed thereon by a solution coating method. Are laminated 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.

In the EL device of the present invention, for example, as shown in FIG. 2, the mixed layer 3a in which the component of the buffer layer can be confirmed to have diffused into a part of the thick film dielectric layer 4 on the substrate side.
It may have a region.

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 for the lower electrode layer, a material which has high conductivity, is not damaged during 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 addition, gold liquid (liquid gold, gold resinat
e, bright gold) may be used. The material called gold solution or water gold is usually prepared by adding gold to a terpene-based solvent in the form of an organometallic compound in an amount of 4 to 25.
% And is a brown viscous liquid. By using this gold solution, a very thin and dense gold film of 50 to 500 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 has been 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 is required 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 during 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.

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. Further, the relative dielectric constant is preferably 1000 or more.

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
a dielectric or ferroelectric material having a perovskite structure such as b (Zr _x Ti _1-x ) O ₃ or Pb (Mg _1/3 Nb _2/3 ) O
₃ , a perovskite relaxor-type ferroelectric material represented by ₃ or the like, a bismuth layered compound represented by Bi ₄ Ti ₃ O ₁₂ , 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
Indicates that the melting point of lead oxide is as low as 888 ° C.
Oxide-based materials such as SiO_Two And CuO, Bi_TwoO_Three ,
Fe_TwoO _Three 700 ° C to 800 ° C 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) O_ThreePerovskite dielectric materials such as
b (Mg_1/3Ni_2/3) O_ThreeComposite perovs represented by
Kytriluxer type ferroelectric material, PbNbO₆Etc.
Typical tungsten bronze type ferroelectric materials
I can do it. These are common materials such as alumina ceramics.
800-900 which is the upper limit temperature of ceramic substrate
At a sintering temperature of 1000 ° C
A dielectric 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 an MOM bond formed by hydrolysis and polycondensation is applied to a substrate. And baking to form a film. 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 sol-gel method and the MOD method, since the elements constituting the dielectric are uniformly mixed in the order of sub-μm or less, the solution coating and baking method is essentially the same as the dielectric formation by the thick film 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, so that the dielectric layer is thickly formed in the concave portion of the substrate. Since a thin layer is formed on the convex portion, the step on the surface of the substrate is flattened, and the surface flatness of the thick ceramic dielectric layer of the EL element is remarkably improved and is formed thereon. The point is that the uniformity of the thin film light emitting layer can be greatly improved.

The thickness of the dielectric layer formed by the solution coating baking method is at least 0.5 μm, 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. 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.

The high dielectric constant layer formed by the solution coating and firing method needs to have a large thickness and a high dielectric constant. As such a high dielectric constant material, for example, BaTi
O ₃ , (Ba _x Ca _1-x ) TiO ₃ , (Ba _x Sr _1-x ) T
a dielectric or ferroelectric material having a perovskite structure such as iO ₃ , PbTiO ₃ , Pb (Zr _x Ti _1-x ) O ₃ ,
Composite perovskite relaxer-type ferroelectric material represented by Pb (Mg _1/3 Nb _2/3 ) O ₃ or Bi ₄ Ti ₃ O ₁₂
, SrBi ₂ Ta ₂ O ₉ and other bismuth-bismuth layered compounds (Sr _x Ba _1-x ) Nb ₂ O ₆ , PbNbO ₆
Tungsten bronze-type ferroelectric materials, etc. represented by the above-mentioned method. Among these, BaTiO ₃ and PZ
A ferroelectric material having a perovskite structure such as T is preferable since it has a high dielectric constant and can be easily formed at a relatively low temperature.

The material of the light-emitting layer is not particularly limited, but a known material such as Mn-doped ZnS described above 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 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 at the time of the heat treatment may be selected from air, N ₂ , He, Ar, or the like depending on the composition of the light emitting layer and the formation conditions.

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 increase the efficiency of 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 element of the present invention has extremely good smoothness on 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.

[0077]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically shown below and described in more detail. Example 1 Screen printing and drying were repeated on a 96% pure alumina substrate using Heraus RP2003 / 237-22% resinate gold paste so that the film thickness after firing was 0.6 μm. Thereafter, firing was performed at 850 ° C. for 20 minutes in an atmosphere in which sufficient air was supplied. The obtained electrode layer was formed by a photo-etching method to a width of 250 μm.
The pattern was patterned into a large number of stripe-shaped patterns each having a length of m and a space of 30 μm.

On the substrate on which the lower electrode was formed, buffer layers of tantalum oxide, barium titanate, and alumina were formed by sputtering. The film forming conditions at this time were as follows. (1) Tantalum oxide (Ta ₂ O ₅ ) Target: Ta ₂ O ₅ Sputter gas: Ar 100 SCCM Reactant gas: O ₂ 15 SCCM Deposition pressure: 0.4 Pa (2) Barium titanate (BaTiO ₃ ) Target: BaTiO ₃ Sputter gas: Ar 60 SCCM Pressure during film formation: 0.5 Pa (3) Alumina (Al ₂ O ₃ ) Target: Al ₂ O ₃ Sputter gas: Ar 100 SCCM Pressure during film formation: 0.4 Pa

When the composition of the obtained film was analyzed, (1) the tantalum oxide film was Ta ₂ O ₅ , (2) the barium titanate film was BaTiO ₃ , and (3) the alumina film was Al ₂ O ₃ . there were. Note that the barium titanate film is heat-treated at 700 degrees Celsius for 10 minutes after the film is formed.

Of these films, tantalum oxide was added in an amount of 0.03
Sample 1 was formed with a thickness of μm, Sample 2 was formed with a thickness of 0.03 μm of barium titanate, and Sample 3 was formed with a thickness of 0.1 μm on tantalum oxide. Also,
Comparative sample 1 was prepared by depositing 0.03 μm alumina.
The sample in which the buffer layer was not formed was designated as Comparative Sample 2. FIG. 7 shows a partial cross-sectional photograph of Sample 1 in this state.

Further, a dielectric ceramic thick film was formed by a screen printing method. As thick film paste, ES
Using a 4210C thick film dielectric paste manufactured by L Company, screen printing and drying were repeated until the film thickness after firing became 20 μm.

After printing and drying, the thick film was fired at 850 ° C. for 20 minutes in an atmosphere supplied with sufficient air using a belt furnace. When this thick film dielectric constant was measured between the lower electrode and the test electrode for measurement formed on the thick film, about 3600
And almost coincided with the bulk value. Therefore, it was found that the effect of the buffer layer on the dielectric constant was almost negligible.

The surface of this thick film dielectric layer was flat, and almost no irregularities higher than the surface roughness derived from the thick film material could be confirmed.
However, a step corresponding to the pattern shape of the lower electrode was confirmed to some extent from the surface, but did not hinder the function of the display. Also, when the substrate on which the thick-film dielectric layer was formed was cut and the cross-section was examined, no evidence of the buffer layer could be confirmed, and it was found by visual inspection that it was completely absorbed by the thick-film layer and was integrated. Was. Sample 1 in this state
FIG. 8 shows a partial cross-sectional photograph of.

On these substrates, a dielectric layer was formed 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 a precursor solution to the above thick film dielectric layer by a spin coating method and baking it at 700 ° C. for 15 minutes was repeated a predetermined number of times.

A basic method for preparing a sol-gel liquid 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.
It was 5 μm. The above sol-gel solution was used as a PZT precursor solution, and application and baking by spin coating were repeated three times to form a PZT dielectric layer having a thickness of about 1.5 μm.

The state of the PZT surface at this time was visually evaluated, and no cracks or the like were found.
On the other hand, the comparative sample 2 in which the buffer layer is not formed is shown in FIG.
The cracks shown in FIG.

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 obtained 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 this time, the ITO thin film of the upper electrode layer is lifted off by using a lift-off method.
It was patterned into a stripe shape having a width of 250 μm and a space of 30 μm.

The obtained device was evaluated for the presence or absence of abnormal light emission such as a bright spot during light emission. Further, among the samples 1, 2, and 3 of the present invention, the comparative sample 1 of alumina, and the comparative sample 2 without forming the buffer layer, those in a relatively good state were selected to obtain light emission characteristics (LV characteristics). evaluated. 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 pulse width of 75 kHz and 100 μs.

[0091] Figure 10 a state when light emission in the present invention a sample of 100 cd / m ^2, the comparative sample 100cd / m ^2, 60
FIGS. 11 and 12 show the states at the time of light emission at 0 cd / m ² . From these figures, it can be seen that non-uniform light emission was observed in the comparative sample, and many base points were observed, particularly at low luminance, whereas uniform light emission was obtained in the sample of the present invention.

FIG. 13 shows the LV characteristics of Invention Sample 1 and Comparative Sample 2, FIG. 14 shows the LV characteristics of Invention Sample 2 and Comparative Samples 1 and 2, and FIG. 14 shows the LV characteristics of Invention Sample 3 and Comparative Sample 2. FIG. 15 shows the -V characteristics. From the LV characteristic graph, it is understood that even if the buffer layer is provided, there is no electrical characteristic deterioration, and the same light emission characteristic as that of the related art can be obtained. In addition, it can be seen that the sample using alumina which does not form a solid solution with the thick film ceramic layer is not integrated with the thick film layer, so that the effect of the buffer layer occurs and the driving voltage is increased.

[0093]

As described above, according to the present invention, in the EL device in which the surface flatness of the thick ceramic dielectric layer is ensured by the sol-gel dielectric layer, the production stability is high, and the EL light emission at the time of driving the device is achieved. A method for manufacturing an EL element without unevenness and an EL element can be provided.

[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 schematic cross-sectional view showing one manufacturing step of the EL element of the present invention.

FIG. 4 is a schematic cross-sectional view showing one manufacturing process of the EL element of the present invention.

FIG. 5 is a schematic sectional view showing one manufacturing process of the EL element of the present invention.

FIG. 6 is a schematic cross-sectional view showing one manufacturing step of the EL element of the present invention.

FIG. 7 is a photograph as a drawing showing a cross-sectional state of the sample 1 of the present invention after formation of a buffer layer.

FIG. 8 is a photograph as a substitute of a drawing, showing a cross-sectional state of the sample 1 of the present invention after formation and firing of a thick-film dielectric layer.

FIG. 9 is a drawing substitute photograph of the surface of a substrate with a PZT dielectric layer (planarization layer) of a comparative sample.

FIG. 10 is a photograph as a substitute of a drawing, in which the light emission state of the invention sample of the embodiment is photographed.

FIG. 11 is a photograph as a substitute of a drawing, in which a light emitting state of a comparative sample of an example is photographed.

FIG. 12 is a photograph as a substitute of a drawing, in which a light emitting state of a comparative sample of an example is photographed.

13 is a graph showing LV characteristics of Comparative Sample 2 and Invention Sample 1. FIG.

FIG. 14 shows L- of Comparative Samples 1 and 2 and Invention Sample 2.
5 is a graph showing V characteristics.

FIG. 15 is a graph showing LV characteristics of Comparative Sample 2 and Invention Sample 3.

FIG. 16 is a schematic sectional view showing a configuration example of a conventional EL element.

FIG. 17 is a schematic sectional view showing a configuration example of a conventional EL element.

[Explanation of symbols]

1 substrate 2 Lower electrode 3 Buffer layer 4 Thick 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 dielectric layer 15 Dielectric layer 16 Thin insulator layer 17 Light-emitting layer 18 Thin insulator layer 19 Transparent electrode layer 20 AC power supply

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Masato Usuda             1-13-1 Nihonbashi, Chuo-ku, Tokyo             ー Decay Corporation (72) Inventor Mutsuko Nakano             1-13-1 Nihonbashi, Chuo-ku, Tokyo             ー Decay Corporation F term (reference) 3K007 AB01 AB08 AB18 CA01 CA02                       CA04 DA03 DA05 EC01 EC04                       FA01

Claims (5)

[Claims] 1. A substrate having electrical insulation, a first 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 on the dielectric layer. An EL element having a multilayer structure of a first dielectric layer in which a layer and a second electrode layer are sequentially laminated, and wherein the dielectric layer is a thick film and a second dielectric layer formed by a solution coating baking method. A manufacturing method, comprising: disposing a buffer layer at least on an electrode layer between a substrate on which the electrode layer is formed and a first dielectric layer;
A method for manufacturing an EL element, comprising firing the dielectric layer. 2. The method for manufacturing an EL element according to claim 1, wherein said buffer layer is formed of a material which is solid-dissolved with said first dielectric layer material by firing to be integrated. 3. The method according to claim 1, wherein the buffer layer is made of tantalum oxide or barium titanate. 4. An EL device manufactured by the method according to claim 1. 5. The EL device according to claim 4, wherein the buffer layer and the first dielectric layer are solid-dissolved and integrated.