JPWO2013128601A1 - ELECTROLUMINESCENT ELEMENT, ELECTROLUMINESCENT ELEMENT MANUFACTURING METHOD, DISPLAY DEVICE, AND LIGHTING DEVICE - Google Patents

Abstract

A substrate, and a stacked portion having a first conductive layer, a dielectric layer, a second conductive layer, a light emitting layer, and a third conductive layer sequentially stacked on the substrate, wherein the dielectric layer includes at least A plurality of contact holes penetrating the dielectric layer are provided, and the first conductive layer and the second conductive layer are electrically connected within the contact hole, and the refractive index of the second conductive layer and the light emitting layer is 1 5 or more and 2.0 or less, and the absolute value of the difference between each refractive index and the refractive index of the dielectric layer is 0.1 or more, from the light emitting surface side where the light emitted from the light emitting layer is extracted. When viewed, (i) at least one continuous light emitting region, (ii) the number of contact holes is 102 or more per light emitting region, and the ratio of the total area occupied by the plurality of contact holes Is less than 0.1 with respect to the area of the light emitting region. The electroluminescent element characterized, the light emitting surface is smooth in the optical unit, the luminance uniformity in the light-emitting surface - of high production to provide easy electroluminescent device.

Description

  The present invention relates to an electroluminescent device, a method for manufacturing an electroluminescent device, a display device, and a lighting device.

  In recent years, devices utilizing the electroluminescence phenomenon have become more important. As such a device, an electroluminescent element in which a light emitting material is formed in a layer form, a pair of electrodes including an anode and a cathode is provided on the light emitting layer, and light is emitted by applying a voltage attracts attention. Yes. Such an electroluminescent device injects holes and electrons from the anode and the cathode, respectively, by applying a voltage between the anode and the cathode, and the injected electrons and holes are combined in the light emitting layer. It emits light using the energy generated by doing so.

  When this electroluminescent element is used as a display device, the light emitting material is self-luminous, and therefore, the response speed as a display device is high and the viewing angle is wide. Further, the structure of the electroluminescent element has an advantage that the display device can be easily thinned. In addition, for example, in the case of an organic light-emitting element using an organic substance as a light-emitting material, it is easy to generate light with high color purity by selecting an organic substance, and therefore, it is possible to take a wide color reproduction range. There is.

  Furthermore, since the electroluminescent element can emit light in its own color and is surface emitting, an application in which the electroluminescent element is incorporated in a lighting device has been proposed.

Conventionally, as an electroluminescent element, an organic layer including a light emitting layer is formed so as to be sandwiched between an anode and a cathode, and a voltage is applied between these electrodes, whereby a light emitting layer in a region where the anode and the cathode overlap each other. Is known to emit light.
Patent Document 1 discloses an organic light emitting element in which one of electrodes is electrically connected to a semiconductor layer, and light is emitted in a light emitting layer sandwiched between the semiconductor layer and the other electrode. In this organic light emitting element, since the emitted light can be extracted from the semiconductor layer to the outside, the electrode can be formed of an opaque material, and a highly conductive and chemically stable metal can be used as the electrode material. it can.

International Publication No. 00/67531 Pamphlet

  Here, an electroluminescent element that electrically connects one of the electrodes to the semiconductor layer and emits light from the light emitting layer sandwiched between the semiconductor layer and the other electrode is formed by patterning the electrode, It is necessary to form a semiconductor layer in contact with. Therefore, when the electrodes are formed in a fine pattern, it becomes difficult to form a smooth semiconductor layer between the electrodes, and light emission in the light emitting surface tends to be uneven. In addition, since a smoothing process is separately required to smooth the semiconductor layer, the manufacturing process becomes complicated, leading to an increase in manufacturing cost.

  In view of the above problems, an object of the present invention is to provide an electroluminescent device that has a smooth light emitting surface in a light emitting portion, has high luminance uniformity within the light emitting surface, and is easy to manufacture.

That is, the present invention includes the following [1] to [13].
[1] A substrate, and a laminated portion having a first conductive layer, a dielectric layer, a second conductive layer, a light emitting layer, and a third conductive layer sequentially laminated on the substrate, and the dielectric The layer is provided with a plurality of contact holes penetrating at least the dielectric layer, and the first conductive layer and the second conductive layer are electrically connected within the contact hole, and the second conductive layer The refractive index of the conductive layer and the light emitting layer is 1.5 or more and 2.0 or less, and the absolute value of the difference between each of the refractive index and the refractive index of the dielectric layer is 0.1 or more, When viewed from the light emitting surface side where light emitted from the light emitting layer is extracted,
(I) having at least one continuous light emitting region;
(Ii) the number of the contact holes, with one of said at emitting region per 10 ² or more, 0.1 or less percentage of the total area of occupied by a plurality of the contact holes with respect to the area of the light-emitting region and An electroluminescent device characterized by comprising:
[2] The electroluminescent element according to item [1], wherein the ratio of the total area occupied by the plurality of contact holes is 0.001 to 0.1 with respect to the area of the light emitting region.
[3] The item [1], wherein the contact hole has a size in which a cross-sectional shape of the contact hole when viewed in plan from the light emitting surface side is included in a circle having a diameter of 0.01 μm to 2 μm. The electroluminescent device according to [2].
[4] The electroluminescent device according to any one of [1] to [3], wherein the contact hole is formed so as to further penetrate the first conductive layer.
[5] Any one of the items [1] to [4], wherein the first conductive layer, the dielectric layer, and the second conductive layer are transparent to the wavelength of light emitted from the light emitting layer. The electroluminescent device according to item.
[6] The electroluminescent device according to any one of items [1] to [5], wherein the second conductive layer and the light emitting layer each have a refractive index larger than that of the dielectric layer. element.
[7] The electroluminescent device according to any one of items [1] to [5], wherein the second conductive layer and the light emitting layer each have a refractive index smaller than that of the dielectric layer. element.
[8] The electroluminescent element according to any one of [1] to [7], wherein the second conductive layer includes a conductive metal oxide or a conductive polymer compound.
[9] The item [1] to [8], further comprising at least one layer selected from a hole transport layer, a hole block layer, and an electron transport layer between the second conductive layer and the third conductive layer. The electroluminescent device according to any one of the above.

[10] A method for manufacturing an electroluminescent device having a continuous light emitting region, the step of sequentially forming a first conductive layer and a dielectric layer on a substrate, and penetrating at least the dielectric layer, one of the with the number formed per light emitting region is 10 ² or more, a plurality of contact holes as percentage of the total area occupied in the light-emitting region is 0.1 or less with respect to the area of the light-emitting region And a refractive index of 1.5 to 2.0 on the dielectric layer while filling the contact hole so as to be electrically connected to the first conductive layer in the contact hole. A step of forming a second conductive layer having an absolute value of a difference between the refractive index and the refractive index of the dielectric layer of 0.1 or more, and refraction on the second conductive layer. If the rate is 1.5 or more and 2.0 or less, Forming a light emitting layer in which an absolute value of a difference between the refractive index and the refractive index of the dielectric layer is 0.1 or more, and further forming a third conductive layer in order. Device manufacturing method.
[11] The method for manufacturing an electroluminescent element according to item [10], wherein the second conductive layer is formed by a coating film forming method.

[12] A display device comprising the electroluminescent element according to any one of items [1] to [9].
[13] An illumination device comprising the electroluminescent element according to any one of items [1] to [9].

  According to the present invention, it is possible to provide an electroluminescent element or the like that has high luminous efficiency and high uniformity of light emission and is easy to manufacture.

It is a fragmentary sectional view explaining an example of the light emission area | region of the electroluminescent element to which this Embodiment is applied. It is a figure explaining the magnitude | size of a contact hole. It is a figure explaining an example of the manufacturing method of an electroluminescent element.

  Hereinafter, embodiments of the present invention will be described in detail. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary. That is, the dimensions, materials, shapes, relative arrangements, and the like of the components described in the embodiments are not intended to limit the scope of the present invention unless otherwise specified, and are merely illustrative examples. . The drawings used are examples for explaining the present embodiment and do not represent actual sizes. The size, positional relationship, and the like of the members shown in each drawing may be exaggerated for clarity of explanation. Further, in this specification, “on” such as “on the layer” is not necessarily limited to the case where it is formed in contact with the upper surface, and is formed on the upper side in a separated manner or between layers. It is used in a sense that includes an intervening layer.

<Electroluminescent element>
FIG. 1 is a partial cross-sectional view illustrating an example of a light emitting region of an electroluminescent element 10 to which the exemplary embodiment is applied.
The electroluminescent element 10 illustrated in FIG. 1 includes a substrate 11 and a stacked portion 110 formed on the substrate 11. The stacked unit 110 includes, from the substrate 11 side, a first conductive layer 12 for injecting holes, an insulating dielectric layer 13, and a second conductive layer 14 covering the top surface of the dielectric layer 13. A light emitting layer 15 that emits light by combining holes and electrons, and a third conductive layer 16 for injecting electrons are sequentially stacked.

  As shown in FIG. 1, the dielectric layer 13 of the electroluminescent element 10 is provided with a plurality of contact holes 17 penetrating the dielectric layer 13. Each contact hole 17 is filled with a component constituting the second conductive layer 14.

  In the present embodiment, the contact hole 17 is filled only with the component of the second conductive layer 14. Thereby, the first conductive layer 12 and the second conductive layer 14 are electrically connected inside the contact hole 17. Therefore, when a voltage is applied between the first conductive layer 12 and the third conductive layer 16, a voltage is applied between the second conductive layer 14 and the third conductive layer 16, and the light emitting layer 15 is Emits light.

  In this case, the surface of the light emitting layer 15 on the substrate 11 side, the surface on the third conductive layer 16 side opposite to the substrate 11 side, or both of these surfaces are outside the electroluminescent element 10. It becomes a light emitting surface from which light is extracted. Further, when viewed from the surface side of the substrate 11 of the electroluminescent element 10 or when viewed from the surface side of the third conductive layer 16 of the electroluminescent element 10, the light emitting layer 15 is continuous. Light is emitted as the light emitting region.

  As another embodiment, the second conductive layer 14 is formed so as to be in contact with the contact hole 17, and another component such as the light emitting layer 15 is further formed, so that the contact hole 17 becomes the second conductive layer. 14 and other components may be filled.

(Substrate 11)
The substrate 11 serves as a support for forming the first conductive layer 12, the dielectric layer 13, the second conductive layer 14, the light emitting layer 15, and the third conductive layer 16. The substrate 11 is typically made of a material that satisfies the mechanical strength required as a support for the electroluminescent element 10.

  As a material of the substrate 11, when light is to be extracted from the substrate 11 side of the electroluminescent element 10 (that is, the surface on the substrate 11 side is a light emitting surface for extracting light), the light emitting layer 15 is used. A material that is transparent to the wavelength of the emitted light is preferred. Specifically, when the light emitted from the light emitting layer 15 is visible light, for example, glass such as soda glass or non-alkali glass; transparent plastic such as acrylic resin, methacrylic resin, polycarbonate resin, polyester resin, nylon resin; silicon Etc.

  In the present embodiment, “transparent to the wavelength of light emitted from the light emitting layer 15” means that it is only necessary to transmit light in a certain wavelength range emitted from the light emitting layer 15. It does not have to be light transmissive over the entire visible light region. However, in this Embodiment, it is preferable that the board | substrate 11 permeate | transmits the light of wavelength 450nm-wavelength 700nm as visible light. Further, the transmittance is preferably 50% or more, and more preferably 70% or more at the wavelength where the emission intensity is maximum.

When it is not necessary to extract light from the surface of the electroluminescent element 10 on the substrate 11 side, the material of the substrate 11 is not limited to a transparent material, and an opaque material can also be used. Specifically, in addition to the above materials, copper, silver, gold, platinum, tungsten, titanium, tantalum, niobium alone, alloys thereof, or materials made of stainless steel can also be used.
Although the thickness of the board | substrate 11 is suitably selected also by the mechanical strength requested | required, Preferably it is 0.1 mm-10 mm, More preferably, it is 0.25 mm-2 mm.

(First conductive layer 12)
The first conductive layer 12 applies a voltage between the third conductive layer 16 and injects holes into the light emitting layer 15 through the second conductive layer 14. That is, in the present embodiment, the first conductive layer 12 is an anode layer. The material used for the first conductive layer 12 is not particularly limited as long as it has electrical conductivity. In the present embodiment, the sheet resistance is usually preferably 1000Ω or less, and more preferably 100Ω or less in the temperature range of −5 ° C. to 80 ° C.

  Examples of materials that satisfy such conditions include conductive metal oxides, metals, alloys, and the like. Here, examples of the conductive metal oxide include ITO (indium tin oxide), IZO (indium zinc oxide), tin oxide, and zinc oxide. Examples of the metal include stainless steel, copper, silver, gold, platinum, tungsten, titanium, tantalum, and niobium. An alloy containing these metals can also be used. Among these materials, ITO, IZO, and tin oxide are preferable as the transparent material used for forming the transparent electrode. Further, a transparent conductive film made of an organic material such as polyaniline or a derivative thereof, polythiophene or a derivative thereof may be used.

The thickness of the first conductive layer 12 is preferably 2 nm to 300 nm in order to obtain high light transmittance when the surface on the substrate 11 side is a light emitting surface for extracting light. Moreover, when it is not necessary to take out light from the board | substrate 11 side, it can form in 2 nm-2 mm, for example.
The substrate 11 can be made of the same material as that of the first conductive layer 12. In this case, the substrate 11 may also serve as the first conductive layer 12.

(Dielectric layer 13)
The dielectric layer 13 is laminated on the first conductive layer 12, and a material transparent to the light emitted from the light emitting layer 15 is used.

  Specific examples of the material constituting the dielectric layer 13 include metal nitrides such as silicon nitride, boron nitride, and aluminum nitride; and metal oxides such as silicon oxide and aluminum oxide. Furthermore, polymer compounds such as polyimide, polyvinylidene fluoride, and parylene can also be used.

  It is preferable that the thickness of the dielectric layer 13 does not exceed 1 μm in order to suppress an increase in electrical resistance between the first conductive layer 12 and the second conductive layer 14. However, if the thickness of the dielectric layer 13 is excessively thin, there is a possibility that the effect of changing the traveling direction of light described later cannot be sufficiently obtained. Therefore, the thickness of the dielectric layer 13 is preferably 10 nm to 500 nm, more preferably 50 nm to 200 nm.

Note that the shape of the contact hole 17 formed through the dielectric layer 13 is not particularly limited, and examples thereof include a cylindrical shape and a quadrangular prism shape.
Further, in the present embodiment, the contact hole 17 is formed so as to penetrate only the dielectric layer 13, but the present invention is not limited to this embodiment. For example, the contact hole 17 may be formed so as to penetrate the first conductive layer 12.

  The dielectric layer 13 can refract the light incident from the light emitting layer 15 through the second conductive layer 14 and increase the light extracted from the electroluminescent device 10 by changing the traveling direction of the light. . For this purpose, the refractive indexes of the second conductive layer 14 and the light emitting layer 15 are 1.5 or more and 2.0 or less, respectively, and the difference between each refractive index and the refractive index of the dielectric layer 13 (Δn ) May be 0.1 or more, respectively. The larger the absolute value of the difference in refractive index (Δn), the more the light traveling direction changes. That is, since more light can be taken out of the electroluminescent element 10, the absolute value of the difference in refractive index (Δn) is more preferably 0.2 or more.

  In addition, the refractive index of the second conductive layer 14 and the refractive index of the light emitting layer 15 are both larger than the refractive index of the dielectric layer 13, or both are smaller than the refractive index of the dielectric layer 13. preferable. That is, for example, it is preferable to use a low refractive index material having a refractive index of 1.4 or less or a high refractive index material of 2.1 or more as a material for forming the dielectric layer 13. Further, when a material having a refractive index of 1.7 or more is used as a material for forming the second conductive layer 14 and the light emitting layer 15, a refractive index of 1.6 or less is used as a material for forming the dielectric layer 13. It is preferable to use these materials. In addition, a refractive index represents the refractive index with respect to a sodium D line | wire (589.3 nm) here. However, when any one material of the dielectric layer 13, the second conductive layer 14, and the light emitting layer 15 is a material that does not transmit light having this wavelength (589.3 nm), the light emitted from the light emitting layer 15 Represents the refractive index with respect to the wavelength at which the intensity becomes maximum.

(Second conductive layer 14)
The second conductive layer 14 is electrically connected to the first conductive layer 12 inside the contact hole 17 and injects holes received from the first conductive layer 12 into the light emitting layer 15. The second conductive layer 14 preferably contains a conductive metal oxide or a conductive polymer. Specifically, it is preferably a transparent conductive film made of an electrically conductive metal oxide such as ITO, IZO or tin oxide having optical transparency; or an organic material such as a conductive polymer compound. In the present embodiment, since the inside of the contact hole 17 is filled with the material forming the second conductive layer 14, the second hole is formed in order to facilitate film formation on the inner surface of the contact hole 17. The conductive layer 14 is preferably formed by coating. Therefore, from this viewpoint, the second conductive layer 14 is particularly preferably a transparent conductive film made of an organic material such as a conductive polymer compound. Note that the second conductive layer 14 and the first conductive layer 12 may be formed using the same material.

The thickness of the second conductive layer 14 is preferably 2 nm to 300 nm in order to obtain high light transmittance when the surface on the substrate 11 side is a light emitting surface for extracting light.
In the present embodiment, a layer that facilitates injection of holes into the light emitting layer 15 (for example, a hole injection layer) is provided on the surface of the second conductive layer 14 that is in contact with the light emitting layer 15. May be. As such a layer, specifically, a 1 nm to 200 nm layer made of a conductive polymer such as a phthalocyanine derivative or a polythiophene derivative, amorphous carbon, carbon fluoride, polyamine compound, or the like; a metal oxide, a metal fluoride, Examples thereof include a layer made of an organic insulating material or the like and having an average film thickness of 10 nm or less.

(Light emitting layer 15)
The light emitting layer 15 includes a light emitting material that emits light when a voltage is applied. As the light emitting material contained in the light emitting layer 15, either an organic material or an inorganic material can be used. In the case of an organic material (light-emitting organic material), both a low molecular compound (light-emitting low molecular compound) and a polymer compound (light-emitting polymer compound) can be used. As the luminescent organic material, a phosphorescent organic compound and a metal complex are preferable.

  In the present embodiment, it is particularly desirable to use a cyclometalated complex from the viewpoint of improving the light emission efficiency of the light emitting layer 15. Examples of cyclometalated complexes include 2-phenylpyridine derivatives, 7,8-benzoquinoline derivatives, 2- (2-thienyl) pyridine derivatives, 2- (1-naphthyl) pyridine derivatives, 2-phenylquinoline derivatives, and the like. Examples of the complex include iridium, palladium, and platinum having a ligand. Among these, iridium complexes are particularly preferable. The cyclometalated complex may have other ligands in addition to the ligands necessary for forming the cyclometalated complex.

  Examples of the light-emitting polymer compound include π-conjugated polymer compounds such as poly-p-phenylene vinylene (PPV) derivatives, polyfluorene derivatives, polythiophene derivatives; low molecular dyes, tetraphenyldiamine, and triphenylamine. Examples thereof include a polymer introduced into a chain or a side chain. A light emitting high molecular compound and a light emitting low molecular weight compound can also be used in combination.

The light emitting layer 15 includes a host material together with the light emitting material, and the light emitting material may be dispersed in the host material. Such a host material preferably has a charge transporting property, and is preferably a hole transporting compound or an electron transporting compound. In addition, a well-known material can be used as a positive hole transport compound or an electron transport compound.
The thickness of the light emitting layer 15 is appropriately selected in consideration of charge mobility, injection charge balance, interference of emitted light, and the like, and is not particularly limited. In the present embodiment, the thickness is preferably 1 nm to 1 μm, more preferably 2 nm to 500 nm, and particularly preferably 5 nm to 200 nm.

(Third conductive layer 16)
The third conductive layer 16 applies a voltage between the first conductive layer 12 and injects electrons into the light emitting layer 15. That is, in the present embodiment, the third conductive layer 16 is a cathode layer.
The material used for the third conductive layer 16 is not particularly limited as long as it has electrical conductivity like the first conductive layer 12. In the present embodiment, a material having a low work function and being chemically stable is preferable. Specifically, materials such as Al; alloys of Al and alkali metals such as AlLi; alloys of Al and Mg such as MgAl alloys; alloys of Al and alkaline earth metals such as AlCa can be exemplified.

However, the material of the third conductive layer 16 is the light emitting surface from which light is extracted from the third conductive layer 16 side of the electroluminescent element 10 (that is, the surface on the third conductive layer 16 side extracts light). For example, it is preferable to use a material that is transparent to the emitted light similar to that of the first conductive layer 12.
The thickness of the third conductive layer 16 is preferably 0.01 μm to 1 μm, and more preferably 0.05 μm to 0.5 μm.

  In the present embodiment, a cathode buffer layer (not shown) is used as the third conductive layer 16 for the purpose of lowering the electron injection barrier from the third conductive layer 16 to the light emitting layer 15 and increasing the electron injection efficiency. You may provide adjacent to. The cathode buffer layer needs to have a work function lower than that of the third conductive layer 16, and a metal material is preferably used. Examples of such metal materials include alkali metals (Na, K, Rb, Cs), Mg and alkaline earth metals (Sr, Ba, Ca), rare earth metals (Pr, Sm, Eu, Yb), or these A compound selected from fluorides, chlorides and oxides of these metals, or a mixture of two or more thereof can be used. The thickness of the cathode buffer layer is preferably 0.05 nm to 50 nm, more preferably 0.1 nm to 20 nm, and even more preferably 0.5 nm to 10 nm.

  Furthermore, in the present embodiment, a layer other than the light emitting layer 15 may be formed between the second conductive layer 14 and the third conductive layer 16. Examples of such a layer include a hole transport layer, a hole block layer, and an electron transport layer. Each of these layers is formed using a known charge transporting material or the like according to each function. The thicknesses of these layers are appropriately selected in consideration of charge mobility, injected charge balance, interference of emitted light, and the like, and are not particularly limited. In the present embodiment, the thickness is preferably 1 nm to 500 nm, more preferably 5 nm to 200 nm.

(Contact hole 17)
FIG. 2 is a diagram for explaining the size of the contact hole 17. FIG. 2A shows, for example, a case where the contact hole 17 is viewed from the vertical direction of the light emitting surface of the light emitting layer 15 with respect to the substrate 11, and the cross-sectional shape is a quadrangle, and FIG. This is a case where the shape is a regular hexagon. In the present embodiment, as shown in FIGS. 2A and 2B, the size of the contact hole 17 is the minimum circle (minimum inclusion circle) that includes the above-described cross-sectional shape when the contact hole 17 is viewed in plan view. ) The diameter of 17a is used.

In the present embodiment, from the viewpoint of increasing the area of the light emitting layer 15 formed on the dielectric layer 13 and increasing the luminance of the electroluminescent element 10, the size of the contact hole 17 is set to be the first conductivity. Smaller is desirable as long as an electrical connection between the layer 12 and the second conductive layer 14 is sufficiently possible.
From such a viewpoint, the diameter of the minimum inclusion circle 17a is preferably 0.01 μm to 2 μm. For example, when the contact hole 17 has a cylindrical shape, the diameter of the column is preferably 0.01 μm to 2 μm.

  In the present embodiment, when the dielectric layer 13 is viewed from the light emitting surface side of the light emitting layer 15, the ratio of the total area occupied by the plurality of contact holes 17 is 0.1 or less with respect to the area of the light emitting region. It is preferable that it is 0.001-0.1. When the ratio of the total area occupied by the plurality of contact holes 17 is within the above-described range, light emission with high luminance can be obtained.

In this embodiment, the number of the contact holes 17 formed in one of the light emitting region comprises at least 10 ² or more, it is preferred that preferably 10 ⁴ or more. However, the number of contact holes 17 is preferably in a range in which the ratio of the area occupied by the contact holes 17 on the light emitting region surface is 0.1 or less, as described above. Since FIG. 1 is a schematic diagram, it does not necessarily represent the ratio of these numerical values.

  In the present embodiment, the plurality of contact holes 17 may be uniformly distributed or non-uniformly distributed in the light emitting region depending on a desired light emission form. In addition, the arrangement of the plurality of contact holes 17 in the light emitting region may be regular or irregular. However, from the viewpoint of manufacturing, it is preferable that the plurality of contact holes 17 are regularly arranged. As an example of the regular arrangement, for example, an arrangement of a cubic lattice or a hexagonal lattice can be given. With such an arrangement, in the electroluminescent element 10 to which the present exemplary embodiment is applied, the light emitting portion is formed on the smooth dielectric layer 13, and the uniformity of light emission in the light emitting region can be improved.

  In the above-described example, the example in which the first conductive layer 12 is an anode layer and the third conductive layer 16 is a cathode layer has been described. However, the present invention is not limited to this. The first conductive layer 12 may be a cathode layer, and the third conductive layer 16 may be an anode layer.

<Method for manufacturing electroluminescent element>
Next, a method for manufacturing the electroluminescent element will be described by taking the case of the electroluminescent element 10 shown in FIG. 1 as an example.

FIG. 3 is a diagram illustrating a method for manufacturing the electroluminescent element 10.
First, as shown in FIG. 3A, the first conductive layer 12 and the dielectric layer 13 are sequentially stacked on the substrate 11. In order to form these layers, resistance heating vapor deposition, electron beam vapor deposition, sputtering, ion plating, CVD, or the like can be used. In addition, when a coating film forming method (that is, a method in which a target material is dissolved in a solvent and then dried) is possible, a spin coating method, a dip coating method, an ink jet method, a printing method, It is also possible to form a film using a method such as a spray method or a dispenser method.

Next, contact holes 17 are formed in the dielectric layer 13. For example, the contact hole 17 can be formed by a method using photolithography.
As shown in FIG. 3B, first, a photoresist solution is applied on the dielectric layer 13, and the excess photoresist solution is removed by spin coating or the like to form a resist layer 71.

  Subsequently, as shown in FIG. 3C, a mask on which a predetermined pattern for forming the contact hole 17 is drawn is put on the photoresist layer 71, and ultraviolet (Ultra violet: UV), electron beam (Electron) The photoresist layer 71 is exposed by, for example, Beam: EB). Here, when the same-size exposure (for example, in the case of contact exposure or proximity exposure) is performed, a pattern of the contact hole 17 that is the same size as the mask pattern is formed. Further, when reduction exposure (for example, exposure using a stepper) is performed, a pattern of contact holes 17 reduced with respect to the mask pattern is formed. Next, when the unexposed portion of the photoresist layer 71 is removed using a developing solution, the photoresist layer 71 in the pattern portion is removed, and a part of the dielectric layer 13 is exposed.

  Next, as shown in FIG. 3D, the exposed portion of the dielectric layer 13 is removed by etching to form a contact hole 17. In this case, a part of the first conductive layer 12 provided below the dielectric layer 13 may also be removed by etching. As the etching, either dry etching or wet etching can be used. Examples of dry etching include reactive ion etching (RIE) and inductively coupled plasma etching. Examples of wet etching include a method of immersing in dilute hydrochloric acid or dilute sulfuric acid. When performing etching, the layer through which the contact hole 17 penetrates can be selected by adjusting the etching conditions (for example, processing time, gas used, pressure, substrate temperature, etc.).

  The contact hole 17 can also be formed by a nanoimprint method. Specifically, after the photoresist layer 71 is formed on the dielectric layer 13, a mask having a convex pattern drawn on the surface of the photoresist layer 71 is pressed with pressure. In this state, the resist layer 71 is cured by applying heat or light irradiation or heating and light irradiation to the photoresist layer 71. Next, when the mask is removed, the contact hole 17 pattern corresponding to the convex pattern of the mask is formed on the surface of the photoresist layer 71. Subsequently, the contact hole 17 is formed by performing the etching described above.

  Next, as illustrated in FIG. 3E, the second conductive layer 14, the light emitting layer 15, and the third conductive layer 16 are sequentially stacked on the dielectric layer 13 in which the contact holes 17 are formed. These layers are formed by a method similar to the method for forming the first conductive layer 12 or the dielectric layer 13. In the present embodiment, the second conductive layer 14 is preferably formed by a coating film forming method. When the coating film forming method is employed, the material constituting the second conductive layer 14 can be easily filled in the contact hole 17.

  The electroluminescent element 10 can be manufactured through the above steps. In addition, it is preferable to use the electroluminescent element 10 stably for a long period of time and to attach a protective layer or a protective cover (not shown) for protecting the electroluminescent element 10 from the outside. As the protective layer, polymer compounds, metal oxides, metal fluorides, metal borides, silicon compounds such as silicon nitride and silicon oxide, and the like can be used. And these laminated bodies can also be used. Further, as the protective cover, a glass plate, a plastic plate whose surface has been subjected to low water permeability treatment, a metal, or the like can be used. For such a protective cover, it is preferable to employ a method in which a thermosetting resin or a photocurable resin is attached to the element substrate and sealed. At this time, it is preferable to use a spacer because a predetermined space can be maintained and the electroluminescent element 10 can be prevented from being damaged. If an inert gas such as nitrogen, argon or helium is sealed in this space, it becomes easy to prevent oxidation of the third conductive layer 16 provided on the outermost side. Furthermore, by installing a desiccant such as barium oxide in this space, the damage given to the electroluminescent element 10 by moisture adsorbed in the series of manufacturing steps described above is reduced.

The electroluminescent element 10 to which this exemplary embodiment is applied can be used for a display device, a lighting device, and the like, for example.
Although it does not specifically limit as a display apparatus, For example, what is called a passive matrix type display apparatus is mentioned. A passive matrix type display device is usually formed on a display device substrate, a plurality of anode wirings arranged in parallel on the display device substrate and made of ITO (Indium Tin Oxide) or the like, and an end of the anode wiring. An anode auxiliary wiring electrically connected to the anode wiring, a plurality of cathode wirings arranged so as to be orthogonal to the anode wiring and made of Al or an Al alloy, and a cathode wiring formed on an end of the cathode wiring; A plurality of electrically connected cathode auxiliary wires, an insulating film formed so as to cover the anode wires, and a plurality of cathode wires formed on the insulating film along a direction perpendicular to the anode wires to spatially separate the plurality of cathode wires. Cathode partition walls. The insulating film is provided with a rectangular opening so as to expose a part of the anode wiring, and the plurality of openings are arranged in a matrix on the anode wiring.

In this opening, the electroluminescent element 10 is provided between the anode wiring and the cathode wiring. Each opening serves as a pixel, and a display area is formed corresponding to the opening. The display device substrate is bonded to the sealing plate via a sealing material, and the space where the electroluminescent element 10 is provided is sealed.
The display device having such a structure can supply a current to the electroluminescent element 10 via the anode auxiliary wiring and the cathode auxiliary wiring by the driving device, thereby causing the light emitting layer to emit light and emitting light. An image can be displayed on the display device by controlling light emission and non-light emission of the electroluminescent element corresponding to the predetermined pixel by the control device.

  Further, the lighting device normally supplies a current between the first conductive layer 12 and the third conductive layer 16 of the electroluminescent element 10 by a lighting circuit having a DC power supply and a control circuit therein, The light emitting layer 15 emits light. Then, the light emitted from the light emitting layer 15 is taken out through the substrate 11 and used as illumination light. The light emitting layer 15 may be made of a light emitting material that emits white light, and an electroluminescent element using a light emitting material that emits green light (G), blue light (B), and red light (R). A plurality of 10 may be provided, and their combined light may be white.

  Hereinafter, the present invention will be described in more detail based on examples. However, the present invention is not limited to the following examples.

(Production of electroluminescent device and evaluation of characteristics)
A voltage is applied to each of the electroluminescent devices manufactured in Examples 1 to 3 and Comparative Examples 1 and 2 using a direct current power source (manufactured by Keithley Instruments Co., Ltd., model SM2400), and lighted at an average luminance of 300 cd / m ^2. The light emission efficiency (cd / A) and drive voltage (V) were measured. The measurement results are shown in Table 1. In Table 1, the refractive index of each layer constituting the electroluminescent element, the number (number) of contact holes per light emitting region, and the ratio (occupancy) in the light emitting region are also shown.

Example 1
The electroluminescent element 10 was produced by the following method.
First, on a glass substrate made of quartz glass (substrate 11: 25 mm square, thickness 1 mm), a first conductive film made of an ITO film having a thickness of 150 nm is formed using a sputtering apparatus (E-401s manufactured by Canon Anelva Co., Ltd.). The layer 12 and a dielectric layer 13 made of a silicon dioxide (SiO ₂ ) film having a thickness of 50 nm were sequentially stacked. Subsequently, a photoresist (AZ Electronic Materials, Inc .: AZ1500) layer having a thickness of about 1 μm was formed on the dielectric layer 13 by spin coating.

Subsequently, a mask A corresponding to a pattern in which circles (thickness: 3 mm) are used as base materials and circles are arranged in a hexagonal lattice shape is manufactured, and using a stepper exposure apparatus (manufactured by Nikon, model NSR-1505i6), 1/5 The photoresist layer was exposed to scale. Next, the exposed photoresist layer was developed with a 1.2% solution of tetramethylammonium hydroxide (TMAH): (CH ₃ ) ₄ NOH), and the photoresist layer was then patterned. Heat was applied for 10 minutes at (post bake treatment).

Next, using a reactive ion etching apparatus (RIE-200iP, manufactured by Samco Corporation), CHF ₃ is used as a reaction gas, and the reaction is performed for 18 minutes under the conditions of pressure 0.3 Pa and output Bias / ICP = 50/100 (W). The photoresist layer was dry-etched. Next, the resist residue was removed with a resist removing solution, and a plurality of contact holes 17 penetrating the dielectric layer 13 made of the SiO ₂ layer were formed. The contact holes 17 have a cylindrical shape with a diameter of 1 μm, and are formed on the entire surface of the dielectric layer 13 in a hexagonal lattice pattern with a pitch of 4 μm.

  Subsequently, a water suspension of a mixture of poly (3,4-ethylenedioxythiophene) (PEDOT) and polystyrene sulfonic acid (PSS) on the dielectric layer 13 (PEDOT: PSS = 1: 6 by mass ratio). A liquid (content 1.5% by mass) was applied by spin coating (rotation speed: 3000 rpm), dried at 140 ° C. for 1 hour in a nitrogen atmosphere, and a second layer having a thickness of 20 nm on the dielectric layer 13. The conductive layer 14 was formed. The refractive index of the second conductive layer 14 was 1.5. The refractive index represents the refractive index with respect to the sodium D line (589.3 nm) (hereinafter the same).

Next, a 1.1% by mass xylene solution of the following compound (A) is applied onto the second conductive layer 14 by a spin coating method (rotation speed: 3000 rpm), and at 210 ° C. for 1 hour in a nitrogen atmosphere. It dried and formed the 20-nm-thick hole transport layer.
Subsequently, a xylene solution (solid content concentration: 1.6% by mass) containing the following compound (B), compound (C), and compound (D) at a mass ratio of 9: 1: 90 on the hole transport layer. ) Was applied by spin coating (rotational speed: 3000 rpm) and dried at 140 ° C. for 1 hour in a nitrogen atmosphere to form a light emitting layer 15 having a thickness of 50 nm. The refractive indexes of the hole transport layer and the light emitting layer 15 were both 1.7.

  Furthermore, a cathode buffer layer (thickness 4 nm) made of sodium fluoride and a third conductive layer 16 (thickness 130 nm) made of aluminum are sequentially formed on the light emitting layer 15 by vapor deposition, and electroluminescent A nescent element 10 was produced.

The produced electroluminescent element 10 has a light emitting surface on the substrate 11 side of the light emitting layer 15 and has one continuous light emitting region. Further, when the electroluminescent element 10 was observed from the light emitting surface side (plan view), the number of the plurality of contact holes 17 in the light emitting region was about 2 × 10 ⁷ . The ratio of the total area occupied by the plurality of contact holes 17 to the area of the light emitting region was 0.057. The refractive index of the first conductive layer 12 made of ITO was 1.8, and the refractive index of the dielectric layer 13 made of SiO ₂ was 1.4.

(Example 2)
The composition of the light emitting layer 15 is set to the following compound (E): compound (F): compound (G): compound (D) = 10: 0.4: 0.6: 89 (mass ratio), and the others are carried out. An electroluminescent device was fabricated under the same conditions as in Example 1. The produced electroluminescent element has a light emitting surface on the substrate 11 side of the light emitting layer 15 and one continuous light emitting region. Further, when this electroluminescent element was observed from the light emitting surface side (plan view), the number of the plurality of contact holes 17 in the light emitting region was about 2 × 10 ⁷ . Further, the ratio of the total area occupied by the contact holes to the area of the light emitting region was 0.057. The light emitting layer 15 had a refractive index of 1.7.

(Example 3)
After forming an ITO film having a thickness of 150 nm as the first conductive layer 12 on a glass substrate (substrate 11) made of quartz glass under the same conditions as in Example 1, the dielectric layer 13 was formed using a sputtering apparatus. A 50 nm-thick niobium pentoxide (Nb ₂ O ₅ ) layer (refractive index 2.0) was sequentially stacked to form a film.
Next, after forming a photoresist layer having a thickness of 1 μm on the Nb ₂ O ₅ layer under the same conditions as in Example 1, a mask corresponding to a pattern in which circles are arranged in a hexagonal lattice using quartz as a base material. Using B, the photoresist layer was exposed to 1/5 scale with a stepper exposure apparatus. Thereafter, the photoresist layer was developed with a 1.2% solution of TMAH, and the photoresist layer was patterned by heating at 130 ° C. for 10 minutes.

Subsequently, using a reactive ion etching apparatus (RIE-200iP manufactured by Samco Corporation), CHF3 is used as the reactive gas, and the reaction is performed for 18 minutes under the conditions of pressure 0.3 Pa and output Bias / ICP = 100/100 (W). The photoresist layer was dry-etched. Thereafter, the reactive gas was changed to a mixed gas of Cl ₃ and SiCl ₄ and reacted for 5 minutes under the conditions of pressure 1 Pa and output Bias / ICP = 200/100 (W), and further the dry etching process was continued. Thereafter, the resist residue was removed with a resist removing solution, and a plurality of contact holes 17 penetrating the Nb ₂ O ₅ layer (dielectric layer 13) and the ITO film (first conductive layer 12) were formed. The contact holes 17 have a columnar shape with a diameter of 0.5 μm, and are arranged in a hexagonal lattice pattern with a pitch of 1.6 μm on the entire surface of the Nb ₂ O ₅ layer and the ITO film.

Next, a 20 nm ITO film was formed as the second conductive layer 14 on the entire surface of the Nb ₂ O ₅ layer and in the contact hole 17 by a sputtering apparatus. The refractive index of the second conductive layer 14 was 1.8.
Subsequently, a hole transport layer, a light emitting layer 15, a cathode buffer layer, and a third conductive layer 16 are sequentially stacked on the second conductive layer 14 under the same conditions as in Example 1, thereby forming an electro A luminescent element was produced.

The produced electroluminescent element has a light emitting surface on the substrate 11 side of the light emitting layer 15 and one continuous light emitting region. Further, when the electroluminescent element was observed from the light emitting surface side (plan view), the number of contact holes 17 in the light emitting region was about 1.4 × 10 ⁸ . Further, the ratio of the total area occupied by the plurality of contact holes 17 to the area of the light emitting region was 0.089.

(Comparative Example 1)
An electroluminescent device was produced under the same conditions as in Example 1 except that the mask C was used as a pattern mask when exposing the photoresist layer.
The produced electroluminescent element has a light emitting surface on the substrate 11 side of the light emitting layer 15 and one continuous light emitting region. Furthermore, it had a plurality of contact holes 17 formed in a cylindrical shape with a diameter of 2.5 μm and arranged in a hexagonal lattice pattern with a pitch of 5 μm on the entire surface of the SiO ₂ layer. When this electroluminescent device was observed from the light emitting surface side (plan view), the number of contact holes in the light emitting region was about 1.4 × 10 ⁷ . Further, the ratio of the total area occupied by the plurality of contact holes 17 to the area of the light emitting region was 0.23.

(Comparative Example 2)
An ITO film having a thickness of 150 nm is formed as the first conductive layer 12 on a glass substrate (substrate 11) made of quartz glass under the same conditions as in Example 1, and then the dielectric layer 13 is formed using a vacuum evaporation apparatus. As a film, a barium fluoride (BaF ₂ ) layer (refractive index of 1.5) having a thickness of 50 nm was sequentially laminated.
Next, a contact hole 17 is formed on the entire surface of the BaF ₂ layer under the same conditions as in Example 1, and then the second conductive layer 14, hole transport layer, light emission under the same conditions as in Example 1. The layer 15, the cathode buffer layer, and the third conductive layer 16 were sequentially stacked.

From the results shown in Table 1, in the electroluminescent device having a plurality of contact holes 17 in the dielectric layer 13 and having a continuous light emitting region on the substrate 11 side of the light emitting layer 15, the second conductive layer 14 and with the refractive index of the light emitting layer 15 is 1.5 or more and 2.0 or less and the absolute value of the difference in refractive index between the dielectric layer 13 is 0.1 or more and, formed 10 ² or more per light emitting area In addition, the electroluminescent device (Examples 1 to 3) in which the ratio of the total area occupied by the plurality of contact holes 17 is 0.1 or less with respect to the area of the light emitting region has a light emission efficiency (cd / A). It is 31 cd / A or more, and it can be seen that the drive voltage (V) is 6 V or less. In all of these, white light having a uniform luminance within the light emitting surface was visually observed.

On the other hand, the electroluminescent element (Comparative Example 1) in which the ratio of the total area occupied by the plurality of contact holes 17 is 0.23 (exceeding 0.1) with respect to the area of the light emitting region is light emitting. It can be seen that the efficiency (cd / A) stops at 28 cd / A and the drive voltage (V) increases to 6.6V.
Furthermore, the electroluminescent element (Comparative Example 2) in which the absolute value of the difference between the refractive index of the second conductive layer 14 and the refractive index of the dielectric layer 13 is 0 (less than 0.1) is the drive voltage (Comparative Example 2). Although V) does not increase, it can be seen that the luminous efficiency (cd / A) remains at 25 cd / A.

DESCRIPTION OF SYMBOLS 10 ... Electroluminescent element, 11 ... Board | substrate, 12 ... 1st conductive layer, 13 ... Dielectric layer, 14 ... 2nd conductive layer, 15 ... Light emitting layer, 16 ... 3rd conductive layer, 17 ... Contact Hall, 17a ... Minimum inclusion circle, 110 ... Laminated part

Claims (13)

A substrate,
A laminated portion having a first conductive layer, a dielectric layer, a second conductive layer, a light emitting layer, and a third conductive layer sequentially laminated on the substrate;
The dielectric layer is provided with a plurality of contact holes penetrating at least the dielectric layer,
The first conductive layer and the second conductive layer are electrically connected within the contact hole;
The refractive index of the second conductive layer and the light emitting layer is 1.5 or more and 2.0 or less, and the absolute value of the difference between the refractive index of each of the second conductive layer and the light emitting layer is 0.1. That's it,
When viewed from the light emitting surface side where light emitted from the light emitting layer is extracted,
(I) having at least one continuous light emitting region;
(Ii) the number of the contact holes, with one of said at emitting region per 10 ² or more, 0.1 or less percentage of the total area of occupied by a plurality of the contact holes with respect to the area of the light-emitting region and An electroluminescent device.   2. The electroluminescent device according to claim 1, wherein a ratio of a total area occupied by the plurality of contact holes is 0.001 to 0.1 with respect to an area of the light emitting region.   3. The contact hole according to claim 1, wherein the contact hole has a size in which a cross-sectional shape when the contact hole is viewed in plan from the light emitting surface side is included in a circle having a diameter of 0.01 μm to 2 μm. Electroluminescent element.   4. The electroluminescent device according to claim 1, wherein the contact hole is further formed so as to penetrate the first conductive layer. 5.   5. The electroluminescent device according to claim 1, wherein the first conductive layer, the dielectric layer, and the second conductive layer are transparent to a wavelength of light emitted from the light emitting layer. Nescent element.   6. The electroluminescent device according to claim 1, wherein the second conductive layer and the light emitting layer each have a higher refractive index than the dielectric layer.   6. The electroluminescent device according to claim 1, wherein the second conductive layer and the light emitting layer each have a refractive index smaller than that of the dielectric layer.   The electroluminescent element according to claim 1, wherein the second conductive layer includes a conductive metal oxide or a conductive polymer compound.   9. The device according to claim 1, further comprising at least one layer selected from a hole transport layer, a hole block layer, and an electron transport layer between the second conductive layer and the third conductive layer. Electroluminescent element. A method of manufacturing an electroluminescent device having a continuous light emitting region,
Forming a first conductive layer and a dielectric layer in order on a substrate;
Through at least the dielectric layer, 0 with the number formed per one of the light emitting region is 10 ² or more, the ratio of the total area occupied in the light-emitting region relative to the area of the light-emitting region. Providing a plurality of contact holes to be 1 or less,
While filling the contact hole so as to be electrically connected to the first conductive layer in the contact hole, the refractive index is 1.5 or more and 2.0 or less on the dielectric layer. Forming a second conductive layer having an absolute value of a difference between the refractive index and the refractive index of the dielectric layer of 0.1 or more;
Light emission having a refractive index of 1.5 or more and 2.0 or less on the second conductive layer, and an absolute value of a difference between the refractive index and the refractive index of the dielectric layer being 0.1 or more. Forming a layer, and further forming a third conductive layer in order.   The method for manufacturing an electroluminescent element according to claim 10, wherein the second conductive layer is formed by a coating film forming method.   A display device comprising the electroluminescent element according to claim 1.   An illuminating device provided with the electroluminescent element of any one of Claims 1 thru | or 9.

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