JP2005216758A - Electroluminescent element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electroluminescent element showing sufficiently excellent luminance and sufficiently suitable for practical application. <P>SOLUTION: This inorganic EL element 100 is provided, on a substrate 2, with: facing electrode pairs; a pair of insulator layers 4 and 6 formed between electrodes 3 and 7 constituting the electrode pairs; three or more layers of phosphor layers 52, 54 and 56 formed between the pair of insulator layers 4 and 6 and stacked along the facing direction of the electrode pairs. The lower insulator layer 4 includes an insulation layer having a film thickness so as to prevent dielectric breakdown from occurring between the lower electrodes 3 and the phosphor layer 5 formed by interposing the insulator layer 4. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electroluminescence (hereinafter referred to as “EL”) element, and more particularly, to an inorganic EL element having a laminated light emitting layer.

  A thin film EL element having a phosphor layer made of an inorganic substance utilizing the EL phenomenon (hereinafter referred to as “inorganic EL element”) has a good characteristic such as a long element life and excellent durability. As such, it is expected to be applied to flat and thin displays.

  The light emission color of such an inorganic EL element is determined by the material of the light emitting layer provided in the element. Conventionally, various materials in which a luminescent center element is doped in a host material have been adopted or proposed as a material for the luminescent layer. As the base material, for example, ZnS, CaS, SrS and the like are widely known, and the emission center element is appropriately selected from, for example, rare earth elements and transition metal elements.

In recent years, inorganic EL elements have been eagerly desired to have high brightness, full color, and whitening. For this purpose, an element structure in which the three primary colors of red (R), green (G), and blue (B) emit light efficiently. Is required. As described in Non-Patent Document 1, as the light emitter layer provided in the inorganic EL element that achieves such full color, (1) laminated type, (2) planar arrangement type, (3) white EL and color A filter stack type and (4) a double substrate type have been studied. Among these, the inorganic EL element including the phosphor layer having the laminated structure (1) can be obtained relatively easily by obtaining a high-resolution one and adjusting the thickness of each layer included in the light-emitting layer. Since there are advantages over inorganic EL elements having other light-emitting layer structures, such as the ability to emit light of the above color, their practical application is eagerly desired.
“Recent Advances in Color EL Display Panels”, Yoshimasa Ono, Display and Imaging, 1994, vol. 3, pp. 159-171

  However, the inorganic EL element having the multilayered phosphor layer structure described in Non-Patent Document 1 sandwiches the phosphor layer in order to obtain a sufficient luminance by applying a sufficient voltage to the phosphor layer. In addition to the electrode pair provided in (1), it has a structure in which electrodes are also provided between the respective layers of the luminous body layer (see page 165, FIG. 7). The inorganic EL element illustrated in Patent Document 1 (hereinafter referred to as “laminated inorganic EL element”) includes not only electrodes between the layers of the light emitting layer, but also dielectric breakdown between the electrodes and the light emitting layer. It is necessary to provide an insulator layer for preventing the electrodes so as to sandwich each electrode. As a result, the multilayer inorganic EL element has a large manufacturing cost, and the film quality deteriorates due to the provision of a very large number of layers, leading to a decrease in yield (decrease in reliability) and practical application. Was unsuitable.

  Moreover, when the present inventors examined in detail about the conventional inorganic EL element other than an inorganic EL element provided with the laminated | stacked light emitting layer mentioned above, such conventional inorganic EL element was fully excellent. It was found that it does not show luminance. That is, the (2) planar arrangement type inorganic EL element described in Non-Patent Document 1 has a substantially small effective area for light emission per emission color, and therefore (3), (4) It was found that each of the inorganic EL elements does not exhibit sufficiently good luminance because part of light emission having a certain wavelength range is absorbed by the filter.

  Therefore, the present invention has been made in view of the above circumstances, and an object thereof is to provide an electroluminescent element that exhibits sufficiently high luminance and is sufficiently suitable for practical use.

  In order to achieve the above object, an inorganic EL element of the present invention includes an opposing electrode pair, a pair of insulator layers provided between the electrodes constituting the electrode pair, and the pair of insulator layers. And three or more light-emitting layers that are stacked along the opposing direction of the electrode pair, and one of the pair of insulator layers is provided with the insulator layer interposed therebetween. And an insulating layer having a predetermined thickness so as not to cause dielectric breakdown between the electrode and the light emitting layer.

  The electroluminescent element of the present invention having such a configuration (hereinafter referred to as “inorganic EL element”) does not include an electrode between the layers constituting the light emitter layer, and is an insulator layer sandwiching the electrodes. It does not have. Therefore, since it is not necessary to form as many layers as the multilayer inorganic EL element described in Non-Patent Document 1 described above, the manufacturing cost is not enormous, the deterioration of the film quality is sufficiently suppressed, and the yield is also good. It will be something. As a result, the inorganic EL element of the present invention is sufficiently excellent for practical use.

  By the way, when three or more light emitter layers are stacked without interposing electrodes between them as in the present invention, the distance between the electrodes sandwiching the light emitter layer is further increased. The drive voltage needs to be higher than before. If it becomes so, in the insulator layer provided in the conventional inorganic EL element, it exists in the tendency for it to become difficult to prevent the dielectric breakdown between an electrode and a light-emitting body layer. In particular, in the conventional insulator layer formed on an electrode when manufacturing an inorganic EL element, the tendency becomes strong. As a result, a bright spot or dark spot is generated in the inorganic EL element, which is not suitable for practical use.

  However, in the inorganic EL element of the present invention, one insulator layer formed on the electrode does not cause dielectric breakdown between the electrode provided on the insulator layer and the light emitter layer. Includes an insulating layer having a predetermined film thickness. Therefore, even when a higher driving voltage than before is applied to the inorganic EL element of the present invention, the occurrence of dielectric breakdown is sufficiently suppressed, so that it is sufficiently suitable for practical use.

  As the above-described insulating layer, for example, a thick film insulator layer can be used. Here, the “thick film insulator layer” refers to an insulator layer formed by a so-called thick film method. That is, it refers to a layer having a predetermined thickness and a predetermined shape formed by printing or applying a powder-containing paste or precursor solution on the lower layer, followed by drying and baking.

The material constituting the insulating layer is preferably one having a relative dielectric constant of 100 to 10,000. By configuring the insulating layer with such a material, a drop in effective voltage applied to the light-emitting layer can be suppressed, so that the luminance of the inorganic EL element can be further improved. From the same viewpoint, the material constituting the insulating layer is made of BaTiO ₃ , PbTiO ₃ , PbNb ₂ O ₆ , PZT, Bi ₄ Ti ₃ O ₁₂ and PMN (Pb (Mg _1/3 Nb _2/3 ) O ₃ ). It is preferable to contain one or more materials selected from the group consisting of:

  In order to further suppress the occurrence of dielectric breakdown, it is preferable that the insulating layer has a thickness of 10 to 30 μm.

  In the inorganic EL element of the present invention, among the three or more light-emitting layers, each of the three or more light-emitting layers emits light of different colors, and emits white light by combining the light emission. Preferably there is. By doing so, the inorganic EL element of the present invention becomes an inorganic EL element that exhibits white light emission with sufficient luminance.

  Moreover, in the inorganic EL element of the present invention, it is preferable that each luminescent color exhibited by each of the light emitting layers has coordinates that mutually surround coordinates (0.3, 0.3) in chromaticity coordinates. Here, “chromaticity coordinates” refers to chromaticity coordinates (x, y) in a CIE chromaticity diagram based on the XYZ color system. In this chromaticity coordinate, the color represented near the coordinates (0.3, 0.3) is white. When each luminescent color exhibited by each of the three or more luminescent layers has coordinates surrounding this coordinate, the inorganic EL element of the present invention emits white light having sufficient luminance by combining the luminescence. It becomes possible.

  Such three or more light emitting layers include a blue light emitting layer mainly made of a blue light emitting material, a red light emitting layer made mainly of a red light emitting material, and a green light emitting layer made mainly of a green light emitting material. Preferably. As a result, a full-color inorganic EL element having sufficient luminance and white light emission with sufficient luminance is obtained. That is, since the inorganic EL element of the present invention having three or more phosphor layers is a laminated type, it is possible to secure a sufficiently effective light emitting area with one light emitting layer and to use a filter. In addition, the absorption of the emitted light is sufficiently suppressed, so that it has sufficient luminance. Further, since each light emitting layer emits light of three primary colors of blue, red, or green, it is possible to realize a very large number of emission colors including these emission colors with sufficient luminance.

  More specifically, the three or more phosphor layers have a total film thickness of 300 to 600 nm, and Eu is contained as a light emission center in a base material mainly composed of Ba, Al, and S. Among them, one in which Cu is contained as a luminescent center in a base material mainly composed of Sr and S, and one in which Ce is contained as a luminescent center in a base material mainly composed of Sr and S A first phosphor layer composed of at least seeds, a matrix material mainly composed of Zn and S containing Mn as an emission center, and a matrix material mainly composed of Ca and S containing Eu as an emission center. In the matrix material mainly composed of Zn and S, Sm is contained as the emission center, and the matrix material mainly composed of Mg, Ga and O is emitting light. A second light emitting layer composed of at least one of those containing Eu as a base material, a base material composed mainly of Zn and S, containing Tb as an emission center, and a base composed mainly of Ca and S A third phosphor layer comprising at least one of a material containing Ce as a luminescent center in a material and a matrix material mainly comprising Sr, Ga and S containing Eu as a luminescent center Are preferably included. By using these materials, it is possible to obtain a light emitting layer having a higher color purity of blue, red, and yellow.

  ADVANTAGE OF THE INVENTION According to this invention, the electroluminescent element which shows the sufficiently outstanding brightness | luminance and is suitable for practical use can be provided.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings as necessary. In the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. Further, the positional relationship such as up, down, left and right is based on the positional relationship shown in the drawings unless otherwise specified. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios.

  First, reference is made to FIG. 1 which is a perspective view showing a main part of the inorganic EL element of the first embodiment of the present invention.

  An inorganic EL element 100 shown in FIG. 1 is a top emission type double-insulated inorganic EL element. On a substrate 2, a lower electrode 3, a lower insulator layer 4, a light emitter layer 5, and an upper insulator layer are provided. 6 and the upper electrode 7 are laminated in this order. The light emitter layer 5 is formed by further laminating a first light emitter layer 52, a second light emitter layer 54, and a third light emitter layer 56 in this order. The lower electrode 3 and the upper electrode 7 are arranged such that one is a row electrode and the other is a column electrode, and their extending directions are orthogonal to each other.

  In the inorganic EL element 100 having such a configuration, the lower electrode 3 and the upper electrode 7 form a matrix electrode, and the light emitter layer 5 at the intersection of the row electrode and the column electrode becomes a pixel. By selectively applying an AC voltage or a pulse voltage from the AC power source 9 to each pixel constituted by the matrix electrode, the luminescent layer 5 emits electroluminescence, and the emitted light is emitted from the upper insulator layer 6 and the upper electrode. 7 is emitted to the outside. Hereinafter, the material which comprises each member of the inorganic EL element 100 is demonstrated.

(Substrate 2)
The substrate 2 is not particularly limited as long as each layer of the inorganic EL element 100 can be formed on the substrate 2 and there is no possibility of contaminating the light emitting layer 5 formed above. It is preferable to have heat resistance that can withstand the annealing temperature in the annealing treatment performed at the time. Examples of the substrate 2 having such characteristics include a ceramic substrate, a glass ceramic substrate obtained by mixing and sintering glass powder using a ceramic material powder as a filler, and a crystallized glass substrate containing an alkaline earth crystallization component.

(Lower electrode 3)
The lower electrode 3 is disposed on the substrate 2 so that a plurality of strip electrodes extend in a certain direction in a striped manner at regular intervals. The constituent material of the lower electrode 3 is not particularly limited as long as it is a material that is known as an electrode of an inorganic EL element. However, the lower electrode 3 exhibits a predetermined high conductivity, and has a high temperature during annealing. It is preferable that it is hard to be damaged by an oxidizing atmosphere. Furthermore, it is more preferable that the reactivity with the light emitting layer 5 formed above is as low as possible. Specifically, the material constituting the lower electrode 3 is preferably a metal material. For example, a noble metal alloy or an alloy containing a noble metal as a main component and a base metal element added is preferable. By using these metal materials, resistance to high temperatures or oxidizing atmospheres can be sufficiently enhanced.

(Lower insulator layer 4)
The lower insulator layer 4 is formed on the lower electrode 3 and includes an insulating layer having a predetermined thickness so as not to cause a dielectric breakdown between the lower electrode 3 and the light emitter layer 5. .

  The predetermined film thickness of the insulating layer varies depending on the constituent material of the lower electrode 3 and the light emitter layer 5, the thickness of the lower electrode 3, the material constituting the insulating layer, and the like. This is preferable because it can ensure the property. Furthermore, since it exists in the tendency which can suppress the drive voltage applied to the inorganic EL element 100 when it has the film thickness of this range, an insulating layer is preferable also from such a viewpoint.

The constituent material of the insulating layer is not particularly limited. For example, it has a perovskite structure such as BaTiO ₃ , (Ba _x Ca _1-x ) TiO ₃ , (Ba _x Sr _1-x ) TiO ₃ , PbTiO ₃ , PZT, and PLZT. (Ferro) dielectric materials, composite perovskite relaxor type ferroelectric materials typified by PMN (Pb (Mg _1/3 Nb _2/3 ) O ₃ ), Bi ₄ Ti ₃ O ₁₂ , SrBi ₂ Ta ₂ A bismuth layered compound typified by O ₉ or the like, a tungsten bronze type ferroelectric material typified by (Sr _x Ba _1-x ) Nb ₂ O ₆ , PbNb ₂ O ₆ or the like is preferably used.

Among these, a ferroelectric material having a perovskite structure such as BaTiO ₃ , PZT, and PMN is more preferable from the viewpoint that a higher dielectric constant can be achieved and firing is relatively easy. Particularly preferred are dielectric materials containing lead atoms. Such a lead-containing dielectric material has a low melting point of lead oxide as low as 888 ° C., and between lead oxide and other oxide materials (for example, SiO ₂ , CuO, Bi ₂ O ₃ , Fe ₂ O _3, etc.). Since a liquid phase is formed at a low temperature of about 600 to 800 ° C., firing at a low temperature is possible by using an appropriate sintering aid, and an extremely high dielectric constant is exhibited.

Examples of such a dielectric material containing lead include a perovskite structure dielectric material such as PZT and PLZT (PbZrO ₃ —PbTiO ₃ solid solution to which La is added), PMN (Pb (Mg _1/3 Nb _2/3 ) O, and the like. ₃ ), a composite perovskite relaxor-type ferroelectric material, and a tungsten bronze-type ferroelectric material typified by PbNb ₂ O ₆ can be preferably used. These can easily form an insulator layer having a relative dielectric constant of 1000 or more at a firing temperature of about 800 ° C., and when using a composite perovskite relaxor type ferroelectric material such as PMN, the relative dielectric constant is 10,000. It is also possible to obtain an insulator exhibiting a high dielectric constant exceeding.

  The relative dielectric constant of the insulating layer is preferably 100 to 10,000 from the viewpoint of ensuring insulation and increasing the effective voltage applied to the light-emitting layer 5. The constituent material may be selected and the content ratio of each constituent material may be adjusted so that the dielectric constant of the insulating layer is within this range.

  The insulating layer may be a thick film insulator layer. Here, the “thick film insulator layer” refers to an insulator layer formed by a so-called thick film method. That is, it refers to a layer having a predetermined thickness and a predetermined shape formed by printing or applying a powder-containing paste or precursor solution on the lower layer, followed by drying and baking. By forming the insulating layer in this manner, the manufacturing cost of the inorganic EL element 100 can be reduced and the mass productivity is excellent as compared with the case where the insulating layer is formed by the vapor phase growth method. .

  The lower insulator layer 4 may be formed by, for example, laminating a thin film made of a known ceramic material on the insulating layer. The thin film may be, for example, a layer for covering the surface of the insulating layer to ensure flatness. In this case, it is preferable that the thickness of the thin film is such that minute irregularities that can occur on the surface of the insulating layer are sufficiently embedded. Specifically, for example, the thickness of the thin film is preferably 0.5 μm or more, more preferably 1 μm or more, and further preferably 2 μm or more. When the main purpose is embedding such fine irregularities, the thickness of the thin film does not need to exceed 10 μm.

  The thin film formed on the insulating layer preferably has a dielectric constant higher than that of the insulating layer, more preferably 100 or more, and even more preferably 500 or more. Examples of the dielectric material exhibiting such a high dielectric constant include the same types of materials as those suitably used for the insulating layer described above, but different from the materials used for the insulating layer, It is more preferable that the material has a higher relative dielectric constant than the material used for the layer.

The lower insulator layer 4 is a thin film for further facilitating the control of the electronic state at the interface with the light emitter layer 5 on the thin film, stabilizing the electron injection into the light emitter layer 5 and increasing its efficiency. May be provided. Specific examples of such thin film constituent materials include rare earth oxides such as yttrium oxide (Y ₂ O ₃ ), silicon oxide (SiO ₂ ), silicon nitride (Si ₃ N ₄ ), and tantalum oxide (Ta ₂ O _5). ), Strontium titanate (SrTiO ₃ ), barium titanate (BaTiO ₃ ), zirconia (ZrO ₂ ), hafnia (HfO ₂ ), silicon oxynitride (SiON), alumina (Al ₂ O ₃ ), aluminum nitride (AlN) ) And gallium nitride (GaN).

(Luminescent layer 5)
The light emitter layer 5 is formed on the lower insulator layer 4, and is formed by laminating a first light emitter layer 52, a second light emitter layer 54, and a third light emitter layer 56 in this order from the bottom. .

  The first light emitter layer 52 is a blue light emitter layer made of a blue light emitting material. As the blue light emitting material, a known blue light emitting material can be used as a light emitting layer material of the inorganic EL element. Among them, a base material mainly composed of Ba, Al and S contains Eu as a light emission center (hereinafter referred to as “BaAlS: Eu”), SrS: Cu and SrS: Ce. It is preferable to use one or more of these materials because the luminance and blue color purity of the first light emitter layer 52 tend to be higher. From the same viewpoint, BaAlS: Eu is particularly preferable among these.

The BaAlS: Eu a, Ba _a Al _b S in consideration of the composition ratio of each element (ion): When expressed as Eu _c, the composition ratio a of Ba is from 0.05 to 0.625, the composition ratio of Al b is 0.025 to 0.63 is preferred. Further, as the addition amount of Eu as the emission center, c is (where c represents the ratio of c in the total element ratio), particularly 0.2 to 1.2, more preferably 0.4. To 1, more preferably 0.6 to 0.8.

  These materials have “high blue color purity”, that is, their emission spectrum has a maximum peak on the shorter wavelength side (higher energy side) than other light emitting materials. It is difficult to obtain such a maximum peak even if an additive substance is contained in another light emitting material. On the other hand, it is possible to shift the maximum peak to the long wavelength side by adding another additive to these materials. Therefore, by providing the blue light emitting layer 52 using these materials, the inorganic EL element 100 of the present embodiment can emit light of various colors that cannot be realized using other materials.

The second light emitter layer 54 is a green light emitter layer made of a green light emitting material. As the green light emitting material, a known green light emitting material can be used as the light emitting layer material of the inorganic EL element. Among them, when ZnS: Tb, ZnS: TbOF, CaS: Ce and / or SrGa ₂ S ₄ : Eu are used, the luminance and green color purity of the second light-emitting layer 54 tend to be higher. ,preferable. From the same viewpoint, among these, ZnS: TbOF is particularly preferable.

The third light emitter layer 56 is a red light emitter layer made of a red light emitting material. As the red light emitting material, a known red light emitting material can be used as the light emitting layer material of the inorganic EL element. Among them, when one or more materials of ZnS: Mn, CaS: Eu, ZnS: Sm, and MgGa ₂ O ₄ : Eu are used, the luminance and red color purity of the third light emitter layer 56 are further increased. This is preferable because it tends to be high. From these viewpoints, ZnS: Mn is particularly preferable among these.

  When the first light emitter layer 52, the second light emitter layer 54, and the third light emitter layer 56 are stacked using the materials exemplified above, the resulting light emitter layer 5 has a wider wavelength range. Since the peak of an emission spectrum can be shown, it is preferable.

  By stacking the first light emitter layer 52, the second light emitter layer 54, and the third light emitter layer 56 by adjusting the ratio of the film thickness, the resulting light emitter layer 5 emits white light. Can be presented. The white light emission corresponds to the vicinity of (0.3, 0.3) in the chromaticity coordinates (x, y), but the respective emission colors based on the above-described light emitting materials have the coordinates (0.3, 0.3, 0.3), it is located at the coordinates surrounding it, so that it is possible to emit white light by combining the layers made of these materials.

Here, “coordinates that mutually surround the coordinates (0.3, 0.3)” means coordinates as described below (see FIG. 2). That is, for example, the coordinates of the light emission colors exhibited by the light emitter layers 52, 54, and 56 included in the light emitter layer 5 are respectively (x ₅₂ , y ₅₂ ), (x ₅₄ , y ₅₄ ), (x ₅₆ , y ₅₆ ). In the chromaticity coordinates, these coordinates are connected by line segments, and the line segment connecting the coordinates (x ₅₂ , y ₅₂ ) and (x ₅₄ , y ₅₄ ) is Sa, and the coordinates (x ₅₄ , y ₅₄ ). A segment connecting the line (x ₅₆ , y ₅₆ ) to Sb, and a line segment connecting the coordinates (x ₅₆ , y ₅₆ ) and (x ₅₂ , y ₅₂ ) to Sc. In this case, in the chromaticity coordinates, if the coordinates (0.3, 0.3) are located on the center side of the triangle formed by the line segments Sa, Sb, and Sc as shown in FIG. (X ₅₂ , y ₅₂ ), (x ₅₄ , y ₅₄ ), and (x ₅₆ , y ₅₆ ) are “coordinates that mutually surround the coordinates (0.3, 0.3)”.

  On the other hand, when it does not correspond to “coordinates that mutually surround the coordinates (0.3, 0.3)”, for example, the coordinates (xa, ya), (xb, yb), (xc, yc) shown in FIG. When the coordinates (0.3, 0.3) are positioned on or around the line segment of the triangle formed by the line segments that connect the coordinates of each other, or the triangle is formed by the line segments that connect the coordinates of each other The case where it is not formed is mentioned.

  Further, by stacking the first light emitter layer 52, the second light emitter layer 54, and the third light emitter layer 56 by adjusting the ratio of the film thickness, the light emitter layer 5 obtained is a so-called paper white. It is possible to exhibit luminescence. The light emission of this paper white is expressed in the vicinity of coordinates (0.35, 0.35) in chromaticity coordinates. The chromaticity coordinates of blue, green, and red light emission are coordinates that also surround the paper white coordinates.

  Although the film thickness of the light-emitting body layer 5 is not specifically limited, It is preferable in it being 300-600 nm, and it is more preferable in it being 400-500 nm. When the thickness of the light emitting layer 5 is less than 300 nm, the light emission efficiency (brightness) tends to decrease, and when it is thicker than 600 nm, the driving voltage tends to increase. Moreover, the film thickness of each layer 52, 54, and 56 contained in the light-emitting body layer 5 is not specifically limited, It is preferable if the film thickness as the light-emitting body layer 5 becomes in the range mentioned above.

(Upper insulator layer 6)
The upper insulator layer 6 is intended to facilitate control of the electronic state at the interface with the light emitter layer 5, stabilize electron injection into the light emitter layer 5, and increase its efficiency. The upper insulator layer 6 does not have to have a function of ensuring the withstand voltage, and the film thickness may be relatively thin, preferably 10 to 1000 nm, more preferably about 20 to 200 nm.

The specific resistance of the upper insulator layer 6 is preferably 10 ⁸ Ω · cm or more, more preferably on the order of 10 ¹⁰ to 10 ¹⁸ Ω · cm. Further, these constituent materials are not particularly limited, but specifically, it is preferable that the constituent materials are composed of substances having a relative dielectric constant of preferably 3 or more. From this point of view, the upper insulator layer 6 includes, for example, silicon oxide (SiO ₂ ), silicon nitride (Si ₃ N ₄ ), tantalum oxide (Ta ₂ O ₅ ), strontium titanate (SrTiO ₃ ), yttrium oxide (Y ₂ O ₃ ), zirconia (ZrO ₂ ) silicon oxynitride (SiON), alumina (Al ₂ O ₃ ), and other metal oxide materials having electrical insulation.

(Upper electrode 7)
The upper electrode 7 is disposed on the upper insulator layer 6 so that a plurality of strip electrodes extend in a planar direction perpendicular to the extending direction of the lower electrode 3 in a striped manner at regular intervals. The upper electrode 7 is made of a transparent conductive material in order to extract light emitted from the upper part of the inorganic EL element 100. As such a transparent conductive material, an oxide conductive material such as In ₂ O ₃ , SnO ₂ , ITO, or ZnO—Al can be used.

(Manufacturing method of inorganic EL element 100)
An example of a method for manufacturing the inorganic EL element 100 described above will be described below. First, the substrate 2 made of the constituent material as described above is prepared. Next, the lower electrode 3 is formed in a stripe shape on the substrate 2 by a printing method, an etching process or the like. Next, the lower insulator layer 4 is formed on the substrate 2 on which the lower electrode 3 is formed. In the case where the lower insulator layer 4 is a thick film insulator layer, the thick film insulator layer is coated with a thick film paste prepared by previously mixing a ceramic material powder with a binder, a solvent, etc. on the substrate 2 and then dried. After forming the film green, the thick film green can be formed by firing, a sol-gel method, a MOD (Metallo-Organic Decomposition) method, or the like.

  Next, a material obtained by processing the material constituting the light emitter layer 5 into a pellet or the like is used as a target, and the first light emitter layer 52, the second light emitter layer 54, and the first light emitter layer 52 are formed on the lower insulator layer 4 by sputtering or vapor deposition. The three light emitter layers 56 are sequentially laminated to form the light emitter layer 5. From the viewpoint of workability at the time of lamination, it is preferably formed by sputtering. In addition, after the light emitting layer 5 is formed, it is preferable to perform annealing treatment under conditions such as an oxidizing atmosphere as necessary from the viewpoint of further improving the light emission efficiency. The annealing treatment can be performed immediately after the formation of the light emitter layer 5, immediately after the formation of the upper insulator layer 6, or after the inorganic EL element 100 is completed. Moreover, it is preferable to control the film thickness of each light emitter layer 52, 54, and 56 included in the light emitter layer 5 as desired by appropriately adjusting the sputtering process time.

  Next, after the upper insulator layer 6 is formed on the phosphor layer 5 by vapor deposition (vapor deposition method) or the like, a striped upper electrode 7 is further formed by vapor deposition, sputtering, or the like. The inorganic EL element 100 is obtained by forming by a known method.

  The inorganic EL element 100 of the present embodiment obtained as described above does not include an electrode that is included in a conventional laminated inorganic EL element between the layers constituting the light emitting layer, and those Insulator layers that sandwich the electrodes are also not provided. Therefore, since it is not necessary to form as many layers as the conventional laminated inorganic EL element, the manufacturing cost is not enormous, the deterioration of the film quality is sufficiently suppressed, and the yield is improved. As a result, the inorganic EL element 100 of the present embodiment is sufficiently excellent for practical use.

  In addition, since the inorganic EL element 100 includes the three light-emitting layers 52, 54, and 56 that exhibit different light emission on the light-emitting layer 5, an inorganic EL element having a light-emitting layer in which two light-emitting layers are stacked; In comparison, more various emission colors can be realized. Moreover, the ratio of the film thickness of each of the light emitter layers 52, 54, and 56 included in the light emitter layer 5 is adjusted for light emission of a color that is difficult to achieve with conventional inorganic EL elements such as paper white. Thus, it can be obtained relatively easily with sufficient luminance.

  Furthermore, the inorganic EL element 100 of this embodiment includes an insulating layer having a predetermined film thickness so that the lower insulator layer 4 does not cause dielectric breakdown between the lower electrode 3 and the light emitter layer 5. Contains. Therefore, even when a higher driving voltage than before is applied to the inorganic EL element 100 of the present embodiment, the occurrence of dielectric breakdown is sufficiently suppressed, so that it is sufficiently suitable for practical use.

  As mentioned above, although preferred embodiment of the inorganic EL element of this invention was described, this invention is not limited to the said embodiment.

  For example, in another embodiment of the inorganic EL element of the present invention, the light emitter layer may include four or more light emitter layers having different emission colors. Specifically, in addition to blue, green, and red, a phosphor layer that emits blue-green and / or orange (orange) light can be included. Examples of the blue-green light emitting material include SrS: Cu, and examples of the orange light emitting material include ZnS: Mn.

  In this case, it is preferable that the light emitting layers having different emission colors have coordinates surrounding the coordinates (0.3, 0.3) in the chromaticity coordinates. Specifically, a convex polygon is formed by a line segment connecting the coordinates of the luminescent colors exhibited by the light emitting layers, and the coordinates (0.3, 0.3) are on the center side of the convex polygon. Preferably it is located. Thereby, the inorganic EL element can exhibit white light emission.

  Moreover, when three or four or more layers of light emitting layers are laminated, a light emitting layer that exhibits the same light emission color among them may be included. In that case, it is preferable that three or more light-emitting layers exhibit different light emission colors, and three or more light-emitting layers that exhibit different light emission colors are mutually coordinated (0.3, 0.3) in chromaticity coordinates. ) Or coordinates surrounding the coordinates (0.33, 0.33).

In the case of using a light-emitting material that easily takes in oxygen, such as BaAlS, the light-emitting material is used in order to prevent oxygen (O) in the insulator layer and / or the atmosphere from being mixed into the light-emitting material during annealing. You may provide the barrier layer which uses ZnS as a constituent material in the one side or both sides of the light-emitting body layer to contain. Thereby, since mixing of O into a light emitting material such as BaAl ₂ S ₄ can be sufficiently suppressed, an inorganic EL element that emits light of a desired color can be obtained.

  Furthermore, there is no restriction | limiting in particular in the order of the lamination | stacking of the light-emitting layer of 3 layers or 4 layers or more. For example, when three light-emitting layers that emit blue, green, and red light are stacked, the order in which these layers are stacked is the order of blue, green, and red from the side of the lower insulator layer, or The reverse order, the order of green, red, blue, or the reverse order, the order of red, blue, green, or the reverse order may be used.

  In addition, the inorganic EL device of still another embodiment of the present invention may contain an additive substance such as Mg in the phosphor layer in order to shift the maximum peak of the emission spectrum, that is, to change the emission color. Good.

  The inorganic EL device according to still another embodiment of the present invention may be provided with a filter such as a color filter on the side opposite to the upper insulator layer of the upper electrode in order to extract light of a desired color. An overcoat may be provided to protect the filter. In this case, the inorganic EL device of the present invention includes three or more layers of light-emitting layers, so that the emission spectrum shows a maximum peak in a wide wavelength range, and the emission intensity (luminance) in that wavelength range. There are relatively few parts that become low. Therefore, when this inorganic EL element uses a filter, it emits light of a wider variety of colors without lowering the luminance as compared with, for example, an inorganic EL element having two luminescent layers having different emission colors. Tend to be able to.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

(Example 1)
First, screen printing and drying were repeated on a 96% purity 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 supplied with sufficient air to obtain a lower electrode. The obtained lower electrode was patterned into a large number of stripe patterns having a width of 340 μm and a space of 20 μm by a photoetching technique.

  Next, a dielectric ceramic thick film was formed as a thick film insulating layer (insulating layer) by screen printing. As the thick film paste, a thick film insulator paste (main material: PMN) manufactured by ESL (trade name: 4210C) was used, and screen printing and drying were repeated so that the film thickness after firing was 15 μm.

  After printing and drying, the thick film was baked at 800 ° C. for 20 minutes in an atmosphere supplied with sufficient air using a belt furnace.

  Next, a PZT dielectric layer was formed as a planarizing layer on the thick film insulator layer using a solution coating and firing method. Specifically, using a PZT sol-gel solution prepared by the following method as a precursor solution, applying this precursor solution to the dielectric layer by a spin coating method and baking at 700 ° C. for 15 minutes. Repeated predetermined times.

  The PZT precursor solution was prepared by heating and stirring 8.49 g of lead acetate trihydrate and 4.17 g of 1,3-propanediol for about 2 hours to obtain a transparent solution. Separately, 3.70 g of zirconium normal propoxide 70% by mass, 1-propanol solution and 1.58 g of acetylacetone were heated and stirred in a dry nitrogen atmosphere for 30 minutes, and 3.14 g of titanium was added thereto. -75 mass% of diisopropoxide bisacetylacetonate, 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 prepare a brown transparent solution. By keeping this solution at 130 ° C. for several minutes, by-products were removed, and the mixture was further heated and stirred for 3 hours to prepare a PZT precursor solution.

The viscosity of the PZT precursor solution was adjusted by diluting with n-propanol. The film thickness of the dielectric layer per single layer was set to about 0.5 μm by adjusting the spin coating conditions and the viscosity of the PZT precursor solution. The PZT dielectric layer having a thickness of about 1.0 μm was formed by repeating application of the PZT precursor solution by spin coating and baking.
Next, a barium titanate layer having a thickness of 200 nm was formed as a thin film dielectric layer by sputtering to obtain a lower insulator layer. The film forming conditions at this time were as follows.
Target: BaTiO ₃
Sputtering gas (flow rate): Ar gas (60 SCCM)
Pressure during film formation: 0.5 Pa
After film formation, heat treatment was performed at 700 ° C. for 10 minutes in an oxygen atmosphere in a heat treatment furnace.

  Subsequently, the phosphor layer was deposited by vapor deposition.

First, ZnS was deposited as a barrier layer using an E gun (electron gun) and a set film thickness of 15 nm. The substrate temperature at this time was 200 degreeC. Continuously, using a BaS powder to which 5 mol% of Eu was added, evaporating with an E gun (electron gun) and simultaneously evaporating Al ₂ S ₃ powder with resistance heating, the first AlCl: Eu made of BaAlS: Eu A phosphor layer was obtained. The substrate temperature at this time was 400 ° C., and the set film thickness was 200 nm. Further, ZnS was continuously formed as a barrier layer, an E gun (electron gun) was used, and a set film thickness was set to 15 nm. The substrate temperature at this time was 200 ° C.

Next, the laminate obtained through the steps so far was heat-treated at 700 ° C. for 2 minutes in a N ₂ gas atmosphere using a lamp annealer (light irradiation annealing treatment apparatus).

Next, a layer made of ZnS: Tb was formed as the second phosphor layer so as to have a thickness of 100 nm by a sputtering method. The film forming conditions at this time were as follows.
Target: ZnS containing 1 mol% of Tb
Sputtering gas (flow rate): Ar gas (160SCCM)
Pressure during film formation: 2.5 Pa

Subsequently, a layer made of ZnS: Mn was formed as a third light emitting layer so as to have a thickness of 100 nm by a sputtering method. The film forming conditions at this time were as follows.
Target: ZnS containing 0.5 mol% of Mn
Sputtering gas (flow rate): Ar gas (160SCCM)
Pressure during film formation: 2.5 Pa

Furthermore, heat treatment was performed at 550 ° C. for 2 minutes in a N ₂ gas atmosphere using a lamp annealer. Next, as an upper insulator layer, an alumina film was formed to a thickness of 50 nm using an E gun (electron gun). The substrate temperature at this time was 150 ° C.

  Then, an inorganic thin film element of Example 1 was obtained by sequentially forming an ITO thin film as an upper electrode by a sputtering method. At that time, the ITO thin film was patterned by a photo-etching method in a stripe shape having a width of 100 μm and a space of 20 μm so as to be orthogonal to the first electrode layer.

  A drive voltage of 120 Hz, a pulse width of 100 μs, and 170 to 200 Vp was applied between the electrodes of the inorganic EL element of Example 1, and luminance and chromaticity coordinates (x, y) in the CIE chromaticity diagram were measured. The results are shown in Table 1. A plot of chromaticity coordinates is shown in FIG.

  Furthermore, the emission spectrum of the inorganic EL element of Example 1 when the applied voltage is 200 Vp is shown in FIG.

  In addition, Table 2 shows chromaticity coordinates of inorganic EL elements each using the first, second, and third light-emitting layers independently.

(Example 2)
Inorganic EL of Example 2 in the same manner as in Example 1 except that the thickness of the second phosphor layer was changed to 80 nm instead of 100 nm and the thickness of the third phosphor layer was changed to 120 nm instead of 100 nm. An element was obtained. A drive voltage of 120 Hz, a pulse width of 100 μs, and 170 to 200 Vp was applied between the electrodes of the obtained inorganic EL element of Example 2, and luminance and chromaticity coordinates (x, y) in the CIE chromaticity diagram were measured. The results are shown in Table 3. A plot of chromaticity coordinates is shown in FIG.

  Comparative example provided with two light-emitting layers in the same manner as in Example 1 except that the second light-emitting layer was not formed and the film thickness of the third light-emitting layer was changed to 200 nm instead of 100 nm. 1 inorganic EL element was obtained. A drive voltage of 120 Hz, a pulse width of 100 μs, and 170 to 200 Vp was applied between the electrodes of the obtained inorganic EL element of Comparative Example 1, and luminance and chromaticity coordinates (x, y) in the CIE chromaticity diagram were measured. The results are shown in Table 4. A plot of chromaticity coordinates is shown in FIG.

  Furthermore, the emission spectrum of the inorganic EL element of Comparative Example 1 when the applied voltage is 200 Vp is shown in FIG.

It is a schematic perspective view which shows the principal part of the inorganic EL element which concerns on embodiment of this invention. It is a schematic diagram of chromaticity coordinates for explaining an inorganic EL element according to an embodiment of the present invention. It is a plot figure which shows the chromaticity coordinate of the inorganic EL element of an Example and a comparative example. 3 is a graph showing an emission spectrum of the inorganic EL element of Example 1. 6 is a graph showing an emission spectrum of an inorganic EL element of Comparative Example 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 ... Board | substrate, 3 ... Lower electrode, 4 ... Lower insulator layer, 5 ... Light-emitting body layer, 6 ... Upper insulator layer, 7 ... Upper electrode, 100 ... Inorganic EL element.

Claims (5)

Opposing electrode pairs;
A pair of insulator layers provided between the electrodes constituting the electrode pair;
A light emitting layer of three or more layers provided between the pair of insulator layers and stacked along the opposing direction of the electrode pair;
One insulator layer formed on the electrode of the pair of insulator layers does not cause dielectric breakdown between the electrode provided on the insulator layer and the light emitting layer. Thus, an electroluminescent element comprising an insulating layer having a predetermined film thickness.   2. The electroluminescent device according to claim 1, wherein the light emission colors exhibited by each of the three or more light-emitting layers have coordinates that surround each other in coordinates (0.3, 0.3) in chromaticity coordinates. .   The three or more light emitting layers include a blue light emitting layer mainly made of a blue light emitting material, a red light emitting layer made mainly of a red light emitting material, and a green light emitting layer made mainly of a green light emitting material. The electroluminescent element according to claim 1.   The blue light-emitting layer is composed of a base material mainly composed of Ba, Al and S containing Eu as a light emission center, and a base material mainly composed of Sr and S containing Cu as a light emission center. 4. The electroluminescent device according to claim 3, wherein the electroluminescent device is composed of at least one selected from the group consisting of Sr and S containing Ce as an emission center. The three or more phosphor layers have a total film thickness of 300 to 600 nm, and are formed by containing Eu as a luminescent center in a base material mainly composed of Ba, Al and S, mainly Sr and S A first material composed of one or more of a material in which Cu is contained as a luminescent center in a base material made of, and a material in which Ce is contained as a luminescent center in a base material mainly made of Sr and S. A phosphor layer;
A base material mainly composed of Zn and S containing Mn as a luminescent center, a base material mainly consisting of Ca and S containing Eu as a luminescent center, a base material mainly consisting of Zn and S A second light-emitting layer made of one or more of a material in which Sm is contained as a light emission center and a material in which Eu is contained in a base material mainly composed of Mg, Ga and O as a light emission center;
A base material mainly composed of Zn and S contains Tb as an emission center, a base material mainly composed of Ca and S contains Ce as an emission center, and mainly Sr, Ga and S A third light-emitting layer made of at least one of those containing Eu as a light emission center in a base material made of
The electroluminescent element according to claim 1, comprising:

Images