JP4646347B2 - Composite substrate and EL device using the same - Google Patents

Description

【００８４】
表１から明らかなように、中間層を設けず、下部電極と誘電体を直接基板上に形成した場合には誘電体表面のクラックによりエレクトロルミネセンス素子とした場合に、発光開始前に素子が破壊してしまった。しかしガラスからなる中間層を設けた場合には誘電体表面にクラックは見られず、発光を観測することができた。また、従来の鉛系の材料を誘電体に用いた場合に比べ、蛍光層の熱処理温度を高めることができるため、発光輝度向上と発光開始電圧の低下が見られた。
【００８５】
【発明の効果】
以上のように本発明によれば、基板と電極の間にガラスを主成分とする中間層を設けることにより、種種の基板材料と誘電体材料の組み合わせにおいて、クラックのない厚膜誘電体をもつ複合基板、およびこれを用いたＥＬ素子を提供することでができる。
【図面の簡単な説明】
【図１】本発明のＥＬ素子の構成例を示す概略断面図である。
【図２】従来のＥＬ素子の構成を示す概略断面図である。
【符号の説明】
１ 基板
２ 中間層
３ 電極（下部電極）
４ 誘電体層
５ 発光層（蛍光層）
６ 誘電体層
７ 電極（上部電極）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a composite substrate provided with a dielectric and an electrode, and an electroluminescence element (EL element) using the composite substrate.
[0002]
[Prior art]
A phenomenon in which a substance emits light when an electric field is applied is called electroluminescence (EL), and an element using this phenomenon is put into practical use as a backlight of a liquid crystal display (LCD) or a watch.
[0003]
The EL element has a structure in which a powder phosphor is dispersed in an organic substance or a hollow and electrodes are provided on the upper and lower sides, and sandwiched between two electrodes and two thin film insulators on an electrically insulating substrate. There is a thin film type element using the thin film phosphor formed in (1). Further, there are a DC voltage driving type and an AC voltage driving type for each driving method. Dispersion EL elements have been known for a long time and have the advantage of being easy to manufacture, but their use has been limited because of their low brightness and short lifetime. On the other hand, the thin film type EL element has characteristics such as high luminance and long life, and has greatly expanded the practical range of the EL element.
[0004]
Conventionally, in thin-film EL devices, a blue plate glass used for liquid crystal displays and PDPs is used as a substrate, and an electrode in contact with the substrate is a transparent electrode such as ITO, and light emitted from the phosphor is extracted from the substrate side. Was the mainstream. As a phosphor material, ZnS added with Mn that emits yellow-orange light has been mainly used from the viewpoint of easiness of film formation and light emission characteristics. In order to produce a color display, it is essential to employ phosphor materials that emit light in the three primary colors of red, green, and blue. These materials include SrS added with blue luminescence Ce and ZnS added with Tm, ZnS added with red luminescence Sm and CaS added with Eu, ZnS added with green luminescence Tb, and CaS added with Ce. Has been raised as a candidate and research continues. However, up to now, there are problems in light emission luminance, light emission efficiency, and color purity, and it has not been put into practical use.
[0005]
As means for solving these problems, it is known that a method of forming a film at a high temperature and a heat treatment at a high temperature after the film formation are promising. When such a method is used, it is impossible to use blue plate glass as the substrate from the viewpoint of heat resistance. Although the use of a heat-resistant quartz substrate has been studied, the quartz substrate is very expensive and is not suitable for applications requiring a large area such as a display.
[0006]
In recent years, as described in JP-A-7-50197 and JP-B-7-44072, an electrically insulating ceramic substrate is used as a substrate, and a thick film dielectric is used in place of a thin film insulator under the phosphor. Development of devices using the body was reported.
[0007]
The basic structure of this element is shown in FIG. The EL device shown in FIG. 2 has a structure in which a lower electrode 12, a thick film dielectric layer 13, a light emitting layer 14, a thin film insulator layer 15, and an upper electrode 16 are sequentially formed on a substrate 11 such as ceramic. Yes. Thus, unlike the conventional structure, the transparent electrode is provided on the upper part in order to take out the light emission of the phosphor from the upper part opposite to the substrate.
[0008]
In this element, the thick film dielectric has a thickness of several tens of μm, which is several hundred to several thousand times that of the thin film insulator. Therefore, there are few dielectric breakdowns caused by pinholes and the like, and there is an advantage that high reliability and high manufacturing yield can be obtained.
[0009]
The voltage drop to the phosphor layer due to the use of a thick dielectric is overcome by using a high dielectric constant material as the dielectric layer. Further, the heat treatment temperature can be increased by using a ceramic substrate and a thick film dielectric. As a result, it has become possible to form a light emitting material exhibiting high light emission characteristics, which was impossible in the past due to the presence of crystal defects.
[0010]
As a condition of the dielectric material used for the thick film dielectric, it is preferable that the dielectric constant and the withstand voltage are high with a high dielectric constant. However, Al, which is generally widely used as a substrate material₂O_Three As a dielectric material, BaTiO is widely used for capacitor materials because of its high dielectric properties._Three When using Al₂O_Three And BaTiO_Three Due to the difference in coefficient of thermal expansion, the dielectric layer cracked during firing, and there was a problem that sufficient withstand voltage could not be obtained when an EL element was obtained.
[0011]
As a condition of the dielectric material used for the thick film dielectric, it is preferable that the dielectric constant and the withstand voltage are high with a high dielectric constant. However, Al, which is generally widely used as a substrate material₂O_Three BaTiO is widely used for capacitor materials because of its high dielectric properties._Three When BaTiO is used, BaTiO_Three There has been a problem of cracks in the dielectric layer. Since the withstand voltage of the dielectric layer is lowered by this crack, when the EL element is manufactured using this composite substrate, the element is easily destroyed. This is considered to be because the difference in thermal expansion between the substrate material and the dielectric material is different, and the dielectric material must be fired at a high temperature. In view of this problem and the necessity of minimizing the reaction of the dielectric material of the substrate material, Japanese Patent Application Laid-Open No. 7-50197, Japanese Patent Publication No. 7-44072, etc., use a lead system having a relatively low firing temperature as a dielectric material. The dielectric materials have been mainly studied.
[0012]
However, it is not preferable to use lead harmful to the human body as a raw material because it increases the manufacturing cost and waste collection cost. Lead-based dielectric materials generally have a firing temperature of BaTiO._Three Since the temperature is lower, the heat treatment temperature of the phosphor layer when an EL element is formed cannot be increased, and sufficient light emission characteristics cannot be obtained.
[0013]
[Problems to be solved by the invention]
An object of the present invention is to provide an intermediate layer made of glass having a working temperature of 1300 ° C. or less between a substrate and an electrode, thereby having a thick film dielectric without cracks in various combinations of substrate materials and dielectric materials. To provide a composite substrate and an EL element using the same.
[0014]
[Means for Solving the Problems]
(1) A composite substrate in which an electrode formed by a thick film method and a dielectric layer are sequentially formed on a substrate,
A composite substrate having an intermediate layer made of glass having a working temperature of 1300 ° C. or lower between the substrate and the electrode.
(2) The composite substrate according to (1), wherein the glass of the intermediate layer is crystallized glass.
(3) The dielectric layer is made of barium titanate (BaTiO_Three The composite substrate according to (1) or (2), which is a ceramic sintered body containing as a main component.
(4) The dielectric layer includes manganese oxide (MnO), magnesium oxide (MgO), tungsten oxide (WO_Three ), Calcium oxide (CaO), zirconium oxide (ZrO)₂ ), Niobium oxide (Nb)₂O_Five ) And cobalt oxide (Co₂O_Three The composite substrate according to (3) above, containing one or more oxides selected from
(5) The dielectric layer is selected from rare earth elements (Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu). The composite substrate according to (3) or (4) above, containing one or more elemental oxides.
(6) The dielectric layer is made of silicon oxide (SiO₂ The composite substrate according to any one of (3) to (5), comprising a glass component comprising:
(7) An EL device having at least a light emitting layer and a second electrode on the composite substrate of any one of (1) to (6) above
(8) The EL device according to (7), further including a second insulator layer between the light emitting layer and the second electrode.
[0015]
[Action]
In the present invention, even when a substrate material and a dielectric material having different coefficients of thermal expansion are used by providing an intermediate layer made of glass having a working temperature of 1300 ° C. or less between the substrate and the electrode, there is no crack and dielectric A composite substrate having a high body layer withstand voltage can be manufactured. Cracks are generated mainly when the dielectric layer is fired due to the difference in thermal expansion coefficient between the substrate material and the dielectric material, but when there is an intermediate layer made of glass, the working temperature of the intermediate layer glass is the dielectric layer. If the temperature is lower than the formation temperature, the intermediate layer absorbs the stress caused by the difference in thermal expansion coefficient between the glass working temperature and the dielectric layer formation temperature during firing of the dielectric layer. For this reason, if the working temperature of the glass of the intermediate layer is sufficiently lower than the formation temperature of the dielectric layer, it is possible to eliminate cracks that normally occur on the surface of the dielectric layer during firing. Al which is widely used as a substrate material in general by providing an intermediate layer with a glass component of an appropriate composition₂O_Three BaTiO is widely used as a capacitor material because of its high dielectric properties and high reliability._Three Even in the case where the occurrence of cracks in the dielectric layer is unavoidable due to the large difference in thermal expansion coefficient and the high firing temperature as in the combination, a composite substrate without cracks can be produced. Therefore, when an electroluminescent element (EL element) is manufactured using this composite substrate, high voltage driving that provides high light emission characteristics is possible. Further, it is not necessary to use a lead-based dielectric material having a low firing temperature as a dielectric as in the prior art, which is advantageous from the viewpoint of preventing environmental pollution.
[0016]
Further, when an EL element is manufactured using a composite substrate having a high firing temperature in this manner, the heat treatment temperature of the phosphor layer can be increased, so that crystal defects in the phosphor layer can be reduced and high emission characteristics can be obtained. it can. This action is particularly effective in forming a SrS phosphor layer to which Ce that generates blue light emission is added.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
The composite substrate of the present invention is a composite substrate in which an electrode and a dielectric layer are sequentially formed on the substrate, and has an intermediate layer made of glass having an operating temperature of 1300 ° C. or less between the substrate and the electrode. is there.
[0018]
Preferably, the dielectric is barium titanate (BaTiO_Three ) Is a ceramic sintered body containing as a main component. This dielectric layer is composed of rare earth oxides, MnO, MgO, WO_Three , SiO₂ , CaO, ZrO₂ , Nb₂O_Five And Co₂O_Three 1 type (s) or 2 or more types selected from may be contained.
[0019]
Thus, by providing the intermediate layer between the substrate and the dielectric layer, the stress between the substrate and the dielectric layer is relieved, and cracks in the dielectric layer can be suppressed. The withstand voltage can be increased. As a result, an EL element using this composite substrate can be driven at a high voltage that provides high light emission characteristics.
[0020]
FIG. 1 shows a cross-sectional view of an electroluminescence element (EL element) using the composite substrate of the present invention. The composite substrate comprises an electrically insulating ceramic or crystallized glass substrate 1, an intermediate layer 2 made of glass, a thick film electrode (first electrode) 3 patterned in a predetermined pattern, and a thick film method thereon. Thus, a multilayer ceramic structure having a dielectric layer (first dielectric layer) 4 made of a high dielectric constant ceramic sintered body is formed.
[0021]
It is preferable that the working temperature of the glass constituting the intermediate layer 2 is sufficiently lower than the temperature at which the dielectric layer is formed. In particular, the working temperature of the glass is preferably 50 ° C. or more lower than the temperature at which the dielectric layer is formed, and more preferably 100 ° C. or less. In addition, although it does not specifically limit as a minimum of working temperature, Usually, it is more than room temperature. Here, the working temperature means that the viscosity of the glass is 10^Four The temperature at which Poise (P) is formed, and the temperature at which the dielectric layer is formed refers to the temperature of firing and heat treatment necessary for forming the dielectric layer.
[0022]
For example, as shown in FIG. 1, the EL element using the composite substrate includes a thin film light emitting layer (fluorescent layer) 5 formed on the dielectric layer of the composite substrate by a vacuum steamer, a sputtering method, a CVD method, etc., a thin film insulating layer. It has a basic structure consisting of (second insulating layer) 6 and transparent electrode (second electrode) 7. Alternatively, a single insulating structure in which the thin film insulating layer is omitted may be employed.
[0023]
The composite substrate of the present invention and the EL element using the composite substrate are characterized in that a thick film can be formed on the substrate without cracking even by using a dielectric material having a coefficient of thermal expansion different from that of the substrate material by employing an intermediate layer. At this time, for example, BaTiO which is fired at a high temperature_Three If it is used, it does not contain lead and is effective from the viewpoint of preventing environmental pollution. In addition, since the composite substrate is baked at a high temperature, when an EL element is manufactured using the composite substrate of the present invention, the heat treatment temperature of the phosphor layer can be increased and high light emission characteristics can be obtained.
[0024]
The material of the intermediate layer is not particularly limited as long as it has the above-mentioned coefficient of thermal expansion and does not easily react with the substrate or the dielectric layer, but it is preferable to use crystallized glass as a main component. .
[0025]
Here, crystallized glass refers to a glass aggregate (a kind of ceramic) that has been once melted, molded, and slowly cooled as glass and then heated again. Specifically, R₂O-CaO-Al₂O_Three-SiO₂ , MgO-CaO-SiO₂ Series, MgO-Al₂O_Three-SiO₂ And the like.
[0026]
In addition to crystallized glass, the intermediate layer may be made of borosilicate glass or the like as a main component glass.
[0027]
The thickness of the glass intermediate layer formed of these materials is preferably about 1 to 100 μm, particularly about 5 to 20 μm. Further, the thermal expansion coefficient of the formed intermediate layer is 1 to 14 ppm / K.^-1Degree, especially 5-12ppm / K^-1The degree is preferred.
[0028]
As a material for the substrate, a substrate having a thick film forming temperature, an EL phosphor layer forming temperature, a heat-resistant temperature or a melting point that can withstand the annealing temperature of the EL element is 600 ° C. or higher, preferably 700 ° C. or higher, particularly 800 ° C. There is no particular limitation as long as an EL element formed thereon can be formed and a predetermined strength can be maintained. Specifically, alumina (Al₂O_Three ), Forsterite (2MgO · SiO₂ ), Steatite (MgO.SiO)₂ ), Mullite (3Al₂O_Three ・ 2SiO₂ ), Beryllia (BeO), aluminum nitride (AlN), silicon nitride (SiN), ceramic substrates such as silicon carbide (SiC + BeO), and heat resistant glass substrates such as crystallized glass. These heat-resistant temperatures are all about 1000 ° C. or higher. Among these, an alumina substrate and crystallized glass are particularly preferable, and beryllia, aluminum nitride, silicon carbide and the like are preferable when thermal conductivity is required.
[0029]
In addition, quartz, a thermally oxidized silicon wafer, etc., such as titanium, stainless steel, Inconel, and iron-based metal substrates can also be used. In the case of using a conductive substrate such as a metal, a structure in which an insulating process is performed or a thick film having electrodes inside is formed on the substrate is preferable.
[0030]
The lower electrode layer as the first electrode is formed on at least the insulated substrate side or in the insulating layer. The electrode layer exposed to the high temperature of the heat treatment together with the light emitting layer when forming the insulating layer is usually used as the main component such as palladium, rhodium, iridium, rhenium, ruthenium, platinum, silver, gold, tantalum, nickel, chromium, titanium, etc. What is necessary is just to use the metal electrode currently used.
[0031]
Further, when Pd, Pt, Au, Ag, or an alloy thereof is used, it can be fired in the atmosphere. BaTiO adjusted to have reduction resistance_Three When sinter is used, firing can be performed in a reducing atmosphere, so that a base metal such as Ni can be used as the internal electrode.
[0032]
The upper electrode layer serving as the second electrode is preferably a transparent electrode having translucency in a predetermined emission wavelength region. In this case, it is particularly preferable to use a transparent electrode such as ZnO or ITO. ITO is usually In₂O_ThreeAnd SnO are contained in a stoichiometric composition, but the amount of O may be somewhat deviated from this. In₂O_ThreeFor SnO₂Is preferably 1 to 20 wt%, more preferably 5 to 12 wt%. Also, In at IZO₂O_ThreeThe mixing ratio of ZnO to is usually about 12 to 32 wt%.
[0033]
Further, the electrode layer may include silicon. The silicon electrode layer may be polycrystalline silicon (p-Si), amorphous (a-Si), or single crystal silicon as necessary.
[0034]
The electrode layer is doped with impurities in order to ensure conductivity in addition to the main component silicon. The dopant used as an impurity may be any dopant that can ensure predetermined conductivity, and a normal dopant used in a silicon semiconductor can be used. Specifically, B, P, As, Sb, Al and the like can be mentioned, and among these, B, P, As, Sb and Al are particularly preferable. The dopant concentration is preferably about 0.001 to 5 at%.
[0035]
As a method for forming an electrode layer using these materials, an existing method such as a vapor deposition method, a sputtering method, a CVD method, a sol-gel method, or a printing and firing method may be used. In the case of producing a structure in which a film is formed, the same method as the dielectric thick film is preferable.
[0036]
A preferable resistivity of the electrode layer is 1 Ω · cm or less, particularly 0.003 to 0.1 Ω · cm, in order to efficiently apply an electric field to the light emitting layer. The film thickness of the electrode layer depends on the material to be formed, but is preferably 50 to 10,000 nm, particularly 100 to 5000 nm, and more preferably about 100 to 3000 nm.
[0037]
As the dielectric thick film material (first insulating layer), a known dielectric thick film material can be used. Further, a material having a relatively large dielectric constant is preferable.
[0038]
For example, materials such as lead titanate, lead niobate, and barium titanate can be used as the main component.
[0039]
The dielectric layer further comprises manganese oxide (MnO), magnesium oxide (MgO), tungsten oxide (WO_Three ), Calcium oxide (CaO), zirconium oxide (ZrO)₂ ), Niobium oxide (Nb)₂O_Five ) And cobalt oxide (Co₂O_Three ) Or one or more oxides selected from the group consisting of rare earth elements (Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb) And an oxide of an element selected from Lu) may be contained as a subcomponent. These subcomponents are the main components, especially BaTiO._Three The content is preferably 50 mol% or less, more preferably 0.004 to 40 mol%, and particularly preferably 0.01 to 30 mol%.
[0040]
The dielectric layer is made of silicon oxide (SiO 2₂ The glass component may be 2 wt% or less, particularly 0.05 to 0.5 wt% or less. By containing a glass component, the sinterability can be improved.
[0041]
Moreover, the following materials and a mixture of two or more of the following materials are suitable.
[0042]
(A) Perovskite type material: PbTiO_Three Pb-based perovskite compounds such as rare earth element-containing lead titanate, PZT (lead zircon titanate), PLZT (lead lanthanum zircon titanate), NaNbO_Three , KNbO_Three NaTaO_Three , KTaO_Three , CaTiO_Three , SrTiO_Three , BaTiO_Three , BaZrO_Three , CaZrO_Three , SrZrO_Three , CdZrO_Three , CdHfO_Three , SrSnO_Three LaAlO_Three , BiFeO_Three Bi-based perovskite compounds, etc. Simple perovskite compounds as described above, and composite perovskite compounds containing three or more metal elements, and composite and layered perovskite compounds.
[0043]
(B) Tungsten bronze type material: lead niobate, SBN (strontium barium niobate), PBN (lead barium niobate), PbNb₂O₆ , PbTa₂O₆ , PbNb_FourO₁₁ , Ba₂KNb_FiveO₁₅ , Ba₂LiNb_FiveO₁₅ , Ba₂AgNb_FiveO₁₅ , Ba₂RbNb_FiveO₁₅ , SrNb₂O₆ , Sr₂NaNb_FiveO₁₅ , Sr₂LiNb_FiveO₁₅ , Sr₂KNb_FiveO₁₅ , Sr₂RbNb_FiveO₁₅ , Ba_ThreeNb_TenO₂₈ , Bi_ThreeNd₁₇O₄₇ , K_ThreeLi₂Nb_FiveO₁₅ , K₂RNb_FiveO₁₅ (R: Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho), K₂BiNb_FiveO₁₅ , Sr₂TlNb_FiveO₁₅ , Ba₂NaNb_FiveO₁₅ , Ba₂KNb_FiveO₁₅ Such as tungsten bronze type oxide.
[0044]
(C) YMnO_Three System material: Hexagonal system YMnO containing rare earth elements (including Sc and Y), Mn and O_Three An oxide with a structure. For example, YMnO_Three , HoMnO_Threeetc.
[0045]
Many of these are ferroelectrics. Hereinafter, these materials will be described.
[0046]
(A) Of the perovskite materials, BaTiO_Three And Sr-based perovskite compounds generally have the chemical formula ABO_Three It is represented by Here, A and B each represent a cation. A is preferably one or more selected from Ca, Ba, Sr, Pb, K, Na, Li, La and Cd, and B is one or more selected from Ti, Zr, Ta and Nb. It is preferable.
[0047]
The ratio A / B in such a perovskite type compound is preferably 0.8 to 1.3, more preferably 0.9 to 1.2.
[0048]
By setting A / B in such a range, it is possible to ensure the insulation of the dielectric, and it is possible to improve the crystallinity, so that the dielectric characteristics or the ferroelectric characteristics can be improved. it can. On the other hand, if A / B is less than 0.8, the effect of improving crystallinity cannot be expected, and if A / B exceeds 1.3, formation of a homogeneous thin film becomes difficult.
[0049]
Such A / B is realized by controlling the film forming conditions. ABO_Three The ratio of O in is not limited to 3. Some perovskite materials have a stable perovskite structure due to oxygen defects or excess oxygen._X In this case, the value of x is usually about 2.7 to 3.3. A / B can be obtained from fluorescent X-ray analysis.
[0050]
ABO used in the present invention_Three As the type of perovskite compound, A¹⁺B⁵⁺O_Three , A²⁺B⁴⁺O_Three , A³⁺B³⁺O_Three , A_X BO_Three , A (B '_0.67B ″_0.33) O_Three , A (B '_0.33B ″_0.67) O_Three , A (B_0.5 ⁺³ B_0.5 ⁺⁵ ) O_Three , A (B_0.5 ²⁺  B_0.5 ^{6 +} ) O_Three , A (B_0.5 ¹⁺ B_0.5 ⁷⁺ ) O_Three , A³⁺(B_0.5 ²⁺ B_0.5 ⁴⁺ ) O_Three , A (B_0.25 ¹⁺B_0.75 ⁵⁺) O_Three , A (B_0.5 ³⁺ B_0.5 ⁴⁺ ) O_2.75, A (B_0.5 ²⁺ B_0.5 ⁵⁺ ) O_2.75Any of these may be used.
[0051]
Specifically, Pb-based perovskite compounds such as PZT and PLZT, NaNbO_Three , KNbO_Three NaTaO_Three , KTaO_Three , CaTiO_Three , SrTiO_Three , BaTiO_Three , BaZrO_Three , CaZrO_Three , SrZrO_Three , CdHfO_Three , CdZrO_Three , SrSnO_Three LaAlO_Three , BiFeO_Three Bi-based perovskite compounds and their solid solutions.
[0052]
The PZT is PbZrO._Three -PbTiO_Three It is a solid solution of the system. The PLZT is a compound in which La is doped into PZT, and ABO_Three (Pb_0.89~_0.91La_0.11~_0.09) (Zr_0.65Ti_0.35) O_Three Indicated by
[0053]
Of the layered perovskite compounds, Bi-based layered compounds are generally
Formula Bi₂ A_m-1 B_m O_{3m + 3}
It is represented by In the above formula, m is an integer of 1 to 5, A is any one of Bi, Ca, Sr, Ba, Pb, Na, K and rare earth elements (including Sc and Y), and B is Ti, Ta And Nb. Specifically, Bi_Four Ti_Three O₁₂, SrBi₂ Ta₂ O₉ , SrBi₂ Nb₂ O₉ Etc. In the present invention, any of these compounds may be used, and these solid solutions may be used.
[0054]
The perovskite type compound preferably used in the present invention is preferably a compound having a high dielectric constant, and NaNbO_Three , KNbO_Three , KTaO_Three , CdHfO_Three , CdZrO_Three , BiFeO_Three Bi-based perovskite compounds, etc., more preferably CdHfO_Three It is.
[0055]
(B) As the tungsten bronze type material, a tungsten bronze type material described in Landoit-Borenstein Vol. 16 of the ferroelectric material collection is preferable. Tungsten bronze type materials generally have the chemical formula A_yB_FiveO₁₅ It is represented by Here, A and B each represent a cation. A is preferably at least one selected from Mg, Ca, Ba, Sr, Pb, K, Na, Li, Rb, Tl, Bi, rare earth and Cd, and B is Ti, Zr, Ta, Nb, It is preferably at least one selected from Mo, W, Fe and Ni.
[0056]
The ratio O / B in such a tungsten bronze type compound is not limited to 15/5. Some tungsten bronze materials form a stable tungsten bronze structure with oxygen defects or excess oxygen, and the ratio O / B is usually about 2.6 to 3.4.
[0057]
Specifically, (Ba, Pb) Nb₂O₆ , PbNb₂ O₆ , PbTa₂O₆ , PbNb_FourO₁₁, SBN (Strontium barium niobate), Ba₂KNb_FiveO₁₅ , Ba₂LiNb_FiveO₁₅ , Ba₂AgNb_FiveO₁₅ , Ba₂RbNb_FiveO₁₅ , SrNb₂O₆ , BaNb₂O₆ , Sr₂NaNb_FiveO₁₅ , Sr₂LiNb_FiveO₁₅ , Sr₂KNb_FiveO₁₅ , Sr₂RbNb_FiveO₁₅ , Ba_ThreeNb_TenO₂₈ , Bi_ThreeNd₁₇O₄₇ , K_ThreeLi₂Nb_FiveO₁₅ , K₂RNb_FiveO₁₅ (R: Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho), K₂BiNb_FiveO₁₅ , Sr₂TlNb_FiveO₁₅ , Ba₂NaNb_FiveO₁₅ , Ba₂KNb_FiveO₁₅ Tungsten bronze type oxides and the like and solid solutions thereof are preferred, and in particular, SBN [(Ba, Sr) Nb₂ O₆ ] Or Ba₂KNb_FiveO₁₅ , Ba₂LiNb_FiveO₁₅ , Ba₂AgNb_FiveO₁₅ , Sr₂NaNb_FiveO₁₅ , Sr₂LiNb_FiveO₁₅ , Sr₂KNb_FiveO₁₅ Is preferred.
[0058]
(C) YMnO_Three System material is chemical formula RMnO_Three It can be expressed as R is preferably at least one selected from rare earth elements (including Sc and Y). YMnO_Three The ratio R / Mn in the system material is preferably 0.8 to 1.2, more preferably 0.9 to 1.1. By setting it in such a range, insulation can be ensured and crystallinity can be improved, so that the ferroelectric characteristics can be improved. On the other hand, in the range where the ratio R / Mn is less than 0.8 and exceeds 1.2, the crystallinity tends to decrease. In particular, in the range where the ratio R / Mn exceeds 1.2, ferroelectricity tends not to be obtained, and there is a tendency to have a paraelectric property, which makes it impossible to apply to an element using polarization. There is. Such R / Mn is realized by controlling the film forming conditions. In addition, R / Mn can be calculated | required from a fluorescent X ray analysis method.
[0059]
YMnO preferably used in the present invention_Three The system material has a hexagonal crystal structure. YMnO_Three There are two types of materials, one having a hexagonal crystal structure and one having an orthorhombic crystal structure. In order to obtain the effect of phase transition, a hexagonal crystal material is preferable. Specifically, the composition is substantially YMnO._Three , HoMnO_Three , ErMnO_Three YbMnO_Three , TmMnO_Three , LuMnO_Three Or a solid solution of these.
[0060]
The resistivity of the dielectric layer thick film is 10⁸ Ω · cm or more, especially 10^Ten-10¹⁸ It is about Ω · cm. A substance having a relatively high dielectric constant is preferable, and the dielectric constant ε is preferably about ε = 100 to 10,000. As a film thickness, 5-50 micrometers is preferable and 10-30 micrometers is especially preferable.
[0061]
The method of forming the dielectric layer thick film is not particularly limited, and a method by which a film having a thickness of 10 to 50 μm can be obtained relatively easily is preferable, but a sol-gel method, a printing firing method, and the like are preferable.
[0062]
In the case of the printing and baking method, the material has an appropriate particle size and is mixed with a binder to obtain a paste having an appropriate viscosity. This paste is formed on a substrate by a screen printing method and dried. The green sheet is fired at an appropriate temperature to obtain a thick film.
[0063]
When the obtained thick film surface has large irregularities and holes as large as 1 μm or more, it is preferable to improve the flatness by polishing or forming a flattening layer thereon if necessary.
[0064]
As a material used for a light emitting layer of an inorganic EL (electroluminescence) element, a material that obtains red light emission, such as ZnS, Mn / CdSSe, and a material that obtains green light emission, such as ZnS: TbOF, ZnS: Tb, emit blue light. As materials for obtaining, SrS: Ce, (SrS: Ce / ZnS) n, CaCa₂S_Four: Ce, SrGa₂S_Four: Ce and the like. In addition, SrS: Ce / ZnS: Mn multilayer films and the like are known as devices that obtain white light emission.
[0065]
In the present invention, as a material used for the fluorescent thin film of such an EL device, the II-S compound, the II-III-sulfur compound, or the rare earth sulfide is mainly an II-S system represented by SrS. Compound or mainly SrGa₂S_Four II-III represented by₂−S_FourCompound (II = Zn, Cd, Ca, Mg, Be, Sr, Ba, rare earth, III = B, Al, Ga, In, Tl) or Y₂S_ThreeRare earth sulfides such as these, and mixed crystals or mixed compounds of a combination of a plurality of components using these compounds are preferred.
[0066]
The composition ratios of these compounds do not strictly take the above values, but have a certain solid solubility limit for each element. Therefore, the composition ratio may be within that range.
[0067]
Usually, in the EL phosphor thin film, a light emission center is added to a base material. The emission center may be added in an existing amount of an existing transition metal or rare earth. For example, rare earth such as Ce and Eu, Cr, Fe, Co, Ni, Cu, Bi, Ag and the like are added to the raw material in the form of metal or sulfide. Since the addition amount differs between the raw material and the thin film to be formed, the composition of the raw material is adjusted so that the thin film becomes the existing addition amount.
[0068]
As a method for forming an EL phosphor thin film using these materials, an existing method such as an evaporation method, a sputtering method, a CVD method, a sol-gel method, or a printing and baking method may be used.
[0069]
The thickness of the light emitting layer is not particularly limited, but if it is too thick, the driving voltage increases, and if it is too thin, the light emission efficiency decreases. Specifically, although it depends on the fluorescent material, it is preferably 100 to 1000 nm, particularly about 150 to 700 nm.
[0070]
In order to obtain a high-intensity sulfide phosphor thin film, a sulfide phosphor having a composition to be formed is formed at a high temperature of 600 ° C. or higher or annealed at a high temperature of 600 ° C. or higher as necessary. Is preferred. In particular, a high temperature process is effective for obtaining a high-luminance blue phosphor. The inorganic EL dielectric thick film of the present invention can withstand such a high temperature process.
[0071]
The inorganic EL element preferably has a thin film insulator layer (second insulating layer) between the electrode layer and the fluorescent thin film (light emitting layer). As a constituent material of the thin film dielectric layer, for example, silicon oxide (SiO 2₂), Silicon nitride (Si_ThreeN_Four ), Tantalum oxide (Ta₂O_Five), Strontium titanate (SrTiO)_Three), Yttrium oxide (Y₂O_Three), Barium titanate (BaTiO)_Three), Lead titanate (PbTiO_Three), PZT, zirconia (ZrO₂), Silicon oxynitride (SiON), alumina (Al₂O_Three), Lead niobate, PMN-PT-based materials, and the like, and multilayers or mixed thin films thereof. Methods for forming an insulating layer with these materials include vapor deposition, sputtering, CVD, sol-gel, An existing method such as a printing baking method may be used. In this case, the thickness of the insulating layer is preferably 50 to 1000 nm, particularly about 100 to 500 nm.
[0072]
Moreover, after forming a thin film dielectric layer (insulating layer) if necessary, the thin film dielectric layer may be formed in a double layer using another material.
[0073]
Furthermore, an electrode layer (second electrode) is preferably formed on the thin film dielectric layer. The electrode material described above is preferably the electrode material described above.
[0074]
By such a method, an EL element can be formed using the composite substrate of the present invention. A high-temperature process of the phosphor thin film becomes possible, and the characteristics of the blue phosphor that has been insufficient in luminance can be greatly improved, so that a full-color EL display can be realized. Furthermore, in the present invention, an insulating thick film having a high density and no cracks can be obtained, so that the dielectric breakdown of the EL element is less likely to occur, and the stability is significantly increased compared to a normal thin film double insulation structure, resulting in higher brightness and lower voltage. Can be achieved.
[0075]
The composite substrate is preferably manufactured by conventional thick film lamination techniques. That is, electrically insulating crystallized glass, or Al₂O_Three A paste made by mixing a glass raw material powder with a binder is formed on a ceramic substrate such as by a thick film forming method such as a screen printing method or a sheet method, and a conductive powder such as Pd or Pt is used as a raw material. The paste is printed as a pattern by screen printing or the like. In addition, powdered BaTiO_Three A thick film is formed using a dielectric paste produced using as a raw material. Alternatively, a green sheet may be formed by casting a dielectric paste, and this may be laminated and pressure-bonded on the electrode. Alternatively, an electrode may be printed on a dielectric green sheet and pressed onto a stress relaxation layer on the substrate.
[0076]
Further, a laminated green sheet made of an intermediate layer, an electrode, and a dielectric may be separately manufactured and thickly deposited on the substrate. A stress relaxation layer having a gradient composition can be formed by sequentially laminating layers having different compositions. The above structure is fired at a temperature suitable for the intermediate layer and the dielectric layer.
[0077]
【Example】
Next, the composite substrate and the EL element of the present invention will be described more specifically with reference to examples.
[0078]
99.6% Al₂O_Three A paste mainly composed of crystallized glass (product name: IP9117, manufactured by Heraeus) was printed on the substrate and dried at 110 ° C. for several minutes. On top of this, a paste made of Pd powder as an electrode was printed in a stripe pattern having a width of 1.5 mm and a gap of 1.5 mm, and dried at 110 ° C. for several minutes.
[0079]
Apart from these, BaTiO_Three MnO, MgO, Y on powder₂O_Three , V₂O_Five , (Ba, Ca) SiO_Three , Li₂SiO_Three Was added at a predetermined concentration and mixed in water. The mixed powder was dried and then mixed with a binder to prepare a dielectric paste. The produced dielectric paste was printed on the substrate printed with the electrode pattern to a thickness of 30 μm, dried, and baked at 1200 ° C. for 2 hours in the air. The thickness of the intermediate layer after firing was 10 μm, and the thickness of the dielectric layer was 10 μm.
[0080]
In order to measure the electrical properties of the dielectric layer, a stripe-shaped Pd electrode pattern having a width of 1.5 mm and a gap of 1.5 mm was printed and dried so as to be orthogonal to the electrode pattern after the dielectric paste was dried. A sample which was operated and baked with the above temperature pattern was prepared separately. The electroluminescence element is formed by sputtering a ZnS phosphor thin film with a thickness of 0.7 μm using a ZnS target doped with Mn with the composite substrate heated to 250 ° C., and then in vacuum for 10 minutes. Heat treated. Next, Si as the second insulating layer_ThreeN_Four An electroluminescent device was formed by sequentially forming an ITO thin film as a thin film and a second electrode by sputtering.
[0081]
The light emission characteristics were measured by extracting an electrode from the printed and fired electrode and ITO transparent electrode of the obtained element structure and applying an electric field of 1 KHz pulse width 50 μs.
[0082]
Table 1 shows the electrical characteristics of the dielectric layer on the composite substrate manufactured as described above and the light emission characteristics of the electroluminescent device manufactured using these composite substrates.
[0083]
[Table 1]

[0084]
As is apparent from Table 1, when the lower electrode and the dielectric are formed directly on the substrate without providing an intermediate layer, when the electroluminescent device is formed by cracks on the dielectric surface, the device is I destroyed it. However, when an intermediate layer made of glass was provided, no cracks were observed on the dielectric surface, and light emission could be observed. Further, since the heat treatment temperature of the fluorescent layer can be increased as compared with the case where a conventional lead-based material is used for the dielectric, the emission luminance is improved and the emission start voltage is reduced.
[0085]
【The invention's effect】
As described above, according to the present invention, by providing an intermediate layer mainly composed of glass between a substrate and an electrode, a combination of various substrate materials and dielectric materials has a thick film dielectric without cracks. It is possible to provide a composite substrate and an EL element using the composite substrate.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing a structural example of an EL element of the present invention.
FIG. 2 is a schematic cross-sectional view showing a configuration of a conventional EL element.
[Explanation of symbols]
1 Substrate
2 Middle layer
3 electrodes (lower electrode)
4 Dielectric layer
5 Light emitting layer (fluorescent layer)
6 Dielectric layer
7 electrode (upper electrode)

Claims (8)

A dielectric layer that will be formed by the electrode and the thick film technique on the substrate a composite substrate are sequentially formed,
The working temperature between the substrate and the electrodes are to have a middle layer consisting of 1300 ° C. or less of the glass,
The heat-resistant temperature or melting point of the substrate is 600 ° C. or higher,
The working temperature of the glass is lower than the temperature at which the dielectric layer is formed,
The dielectric layer is a composite substrate having a thickness of 5 μm to 50 μm .   The composite substrate according to claim 1, wherein the glass of the intermediate layer is crystallized glass. _3. The composite substrate according to claim 1, wherein the dielectric layer is a ceramic sintered body mainly composed of barium titanate (BaTiO ₃ ). The dielectric layer includes manganese oxide (MnO), magnesium oxide (MgO), tungsten oxide (WO ₃ ), calcium oxide (CaO), zirconium oxide (ZrO ₂ ), niobium oxide (Nb ₂ O ₅ ), and cobalt oxide ( The composite substrate according to claim 3, which contains one or more oxides selected from Co ₂ O ₃ ).   The dielectric layer is an oxidation of an element selected from rare earth elements (Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu). The composite substrate according to claim 3 or 4, which contains one or more substances. The composite substrate according to claim 3, wherein the dielectric layer contains a glass component made of silicon oxide (SiO ₂ ).   An EL device having at least a light emitting layer and a second electrode on the composite substrate according to claim 1.   The EL device according to claim 7, further comprising a second insulator layer between the light emitting layer and the second electrode.

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