JP5066814B2 - ELECTROLUMINESCENT ELEMENT AND LIGHTING DEVICE - Google Patents

Description

The present invention relates to an electroluminescence element, and more particularly to an electroluminescence element excellent in light extraction efficiency.
The present invention also relates to a lighting device using the electroluminescence element as a light source.

  In general, in an electroluminescent element used for an electroluminescent display or electroluminescent illumination, holes injected from an anode and electrons injected from a cathode are recombined in an electroluminescent layer, and the emission center is excited by the recombination energy. And has a light emission principle of emitting light.

  FIG. 2 is a schematic cross-sectional view showing a conventional general electroluminescence element, in which an electrode (cathode) 1, an electroluminescence layer 2, a transparent electrode layer (anode) 3A, and a transparent body (transparent substrate) are formed. They are stacked in order.

  In the electroluminescence display, it is preferable that the light emitted from the electroluminescence layer is efficiently extracted, but the light emitted at an angle close to the critical angle among the emitted light is generated between the transparent substrate on the emission surface and the air. The light is totally reflected at the interface and travels while totally reflecting in the plane direction inside the transparent substrate (substrate mode). There is also guided light (thin film mode) that is totally reflected at the interface between the transparent electrode layer and the transparent substrate and travels in the plane direction inside the transparent electrode or inside the transparent electrode and the electroluminescence layer. Will be absorbed and attenuated, and will not be taken out.

  Conventionally, the light extraction efficiency (the ratio of the light emitted from the electroluminescence layer taken out of the electroluminescence layer) taken out from the transparent substrate of the electroluminescence element is as low as about 20% because of these guided lights. It was.

  Conventionally, various studies have been made on the technology for reducing the guided light of the electroluminescence element. For example, in Patent Document 1, a light scattering portion made of a lens sheet is provided on a transparent substrate, or a matte-treated substrate An organic electroluminescence device utilizing the above is described. However, in this technique, the total reflected light at the interface between the transparent body and air is reduced, and the guided light traveling while totally reflecting the inside of the transparent body in the plane direction is reduced, but at the interface between the transparent electrode layer and the transparent substrate. There is a problem that guided light that is totally reflected and proceeds in the plane direction inside the transparent electrode or inside the transparent electrode and the electroluminescence layer cannot be extracted, and the light extraction efficiency cannot be sufficiently increased.

Patent Document 2 describes an information display in which a frustrator element that prevents total internal reflection of light is arranged. However, in this technology, the light extraction efficiency is slightly improved by arranging the frustrator including the bulk diffuser at various locations in the device, but if the uneven interface and the transparent electrode are adjacent, the light emitting surface In this case, a large number of dark spots are generated, which adversely affects the lifetime of the device. Similarly to Patent Document 1, it is not possible to take out guided light that is totally reflected at the interface between the transparent electrode layer and the transparent substrate and proceeds in the plane direction inside the transparent electrode or inside the transparent electrode and the electroluminescence layer. There was a problem that the efficiency could not be increased sufficiently.
Japanese Patent No. 2931111 JP-T-2004-513383

  The present invention relates to an electroluminescence device in which an electrode, an electroluminescence layer, a high refractive index layer, and a translucent body are arranged in this order, and is totally reflected at an interface between the translucent body and air, and the translucent body is oriented in a plane direction. Reduces not only the guided wave that travels but also the guided wave that travels in the plane direction inside the high-refractive index layer or inside the high-refractive index layer and the electroluminescence layer by total reflection at the interface between the high-refractive index layer and the transparent body. Thus, it is an object to provide an electroluminescent element with high light extraction efficiency.

In particular, it is an object of the present invention to provide an electroluminescence element capable of preventing a decrease in luminance at a pixel end portion required for a lighting device using the electroluminescence element as a light source and further imparting directivity of extracted light.
Another object of the present invention is to provide an illumination device using such an electroluminescence element as a light source.

  As a result of intensive studies to solve the above problems, the present inventors have provided a layer having a light scattering function on the light extraction surface side of each of the high refractive index layer and the translucent body, so that the translucent body and air The total reflection at the interface between the high refractive index layer and the high refractive index layer is reflected at the interface between the high refractive index layer and the transparent body. The present inventors have found that it is possible to reduce a guided wave traveling in the plane direction inside the electroluminescence layer, and that the light extraction efficiency of the electroluminescence element can be significantly improved as compared with the prior art.

  Although the details of the working mechanism of the effect of improving the light extraction efficiency by providing a layer having a light scattering function on the light extraction surface side of each of the high refractive index layer and the transparent body are not clear, the high refractive index layer and the light transmission By providing a layer having a light scattering function on each light extraction surface side of the body, it is totally reflected at the interface between the light transmitting body and air, and the guided light travels while being totally reflected in the surface direction inside the light transmitting body. It is presumed that the guided light traveling in the plane direction through the thin film including the electroluminescent layer and the high refractive index layer can be taken out of the electroluminescent element by multiple scattering.

Accordingly, the gist of the present invention is as follows.
(1) In an electroluminescence element in which an electrode, an electroluminescence layer, a high refractive index layer, and a light transmitting body are arranged in this order, a light scattering function is provided on each light extraction surface side of the high refractive index layer and the light transmitting body. Each of these layers having a light scattering function is a layer containing transparent particles, and a layer having a refractive index lower than that of the light transmitting body is provided between the high refractive index layer and the light transmitting body. The layer having a refractive index lower than that of the light transmitting body is on the light extraction surface side of the light extraction surface side of the high refractive index layer and the light extraction surface side of the high refractive index layer is light. In the layer having a scattering function, the refractive index (N _s ) of the transparent particles is 1.8 or more, and the difference ΔN (= N _m −) between the refractive index (N _m ) of the matrix and the refractive index (N _s ) of the transparent particles. N _s ) is −1.8 to −0.3, and light extraction of the transparent body In the layer having the light-scattering function on the surface side, the refractive index (N _s ) of the transparent particles is 1.5, and the difference ΔN between the refractive index (N _m ) of the matrix and the refractive index (N _s ) of the transparent particles N m _{-N s)} is from 0.1 to 0, the high refractive index layer, and an intermediate layer having a refractive index equivalent to that of transparency electrode layer and the transparent electrode layer, the intermediate layer is a transparent electrode layer An electroluminescence element having a refractive index of 1.55 or more on the light extraction surface side .
(2 ) The electroluminescent element according to ( 1 ), wherein the refractive index of the layer having a refractive index lower than that of the translucent material is 1.3 or less .
(3 ) The electroluminescent element as described in (1) to ( 2 ), which is used as a light source for illumination.
( 4 ) The illumination device, wherein the light source is the electroluminescence element according to any one of (1) to ( 3 ).

According to the electroluminescent device of the present invention,
(1) Light extraction efficiency is greatly improved compared to conventional products.
(2) It is possible to reduce changes in emission color and luminance with respect to the viewing angle caused by light interference. In particular, in white light emitting devices (electron transport layer light emitting device, hole transport layer / electron transport layer light emitting device, tandem device), the emission color and the luminance change with respect to the viewing angle are remarkable. This can be greatly reduced.
(3) The accuracy of uniformity of the film thickness of each layer in the electroluminescence element is eased, and the screen of the element, mass production, and cost reduction are facilitated.
(4) The change in the light emission state due to the temperature characteristics and deterioration of the element can be reduced. Therefore, even when partly replacing the deteriorated element in the lighting device, there is no sense of discomfort before and after the replacement.
(5) Uniform light emission can be realized as illumination by suppressing a decrease in luminance at the pixel end in the illumination device.
(6) The light can be extracted with high luminance, and directivity can be imparted to the extracted light.
Such an effect is produced.

  According to such an electroluminescent element of the present invention, a high luminance can be obtained with a low current amount, and thus a long-life element can be provided. In addition, by obtaining high luminance, an electroluminescence element that can be used as a light emitter, for display applications, illumination applications, and the like.

  In particular, the electroluminescence element of the present invention is an electroluminescence element that is most suitable for illumination use because it can suppress a decrease in luminance at the pixel end portion and can impart a directivity of extracted light.

  The electroluminescence device of the present invention is a self-luminous device and can be used for a field emission display or a plasma display having a translucent material, and its industrial utility is very large.

  Embodiments of the electroluminescent element and lighting device of the present invention will be described in detail below, but the description of the constituent elements described below is an example (representative example) of the embodiment of the present invention, and the present invention is Unless it exceeds the gist, these contents are not specified.

[Configuration of electroluminescence element]
The configuration of the electroluminescence element of the present invention will be described with reference to FIG.

  FIG. 1 is a schematic cross-sectional view showing an embodiment of an electroluminescence element of the present invention.

  The electroluminescent element of the present invention includes an electrode 1, an electroluminescent layer 2, a high refractive index layer 3, and a transparent body 4 arranged in this order, and each light extraction surface of the high refractive index layer 3 and the transparent body 4. Layers 5A and 5B having a light scattering function are provided on the side.

  The electroluminescent element of the present invention may have any other layer between the constituent layers as long as the effect of the present invention is not impaired as long as the structure is in this stacking order.

  Below, each component of the electroluminescent element of this invention is demonstrated.

(1) Electrode The electrode 1 normally functions as a cathode. The material used as the cathode is preferably a metal having a low work function or a compound thereof. The cathode is usually formed of aluminum, tin, magnesium, indium, calcium, gold, silver, copper, nickel, chromium, palladium, platinum, magnesium-silver alloy, magnesium-indium alloy, aluminum-lithium alloy, or the like. In particular, it is preferable to form with aluminum.

  The thickness of the cathode is not particularly limited, but is usually 10 nm or more, preferably 30 nm or more, more preferably 50 nm or more, and usually 1000 nm or less, preferably 500 nm or less, more preferably 300 nm or less.

  The cathode can be formed by a vacuum film formation process such as vapor deposition or sputtering.

For the purpose of protecting the cathode made of low work function metal, it is effective to increase the stability of the device by stacking a metal layer with high work function and stable to the atmosphere on the side opposite to the electroluminescent layer. It is. For this purpose, metals such as aluminum, silver, copper, nickel, chromium, gold, platinum are used. Furthermore, the efficiency of the device can be improved by inserting an ultra-thin insulating film (film thickness: 0.1 to 5 nm) such as LiF, MgF ₂ , or Li ₂ O at the interface between the cathode and the electroluminescence layer.

  Note that a cathode may be formed using a transparent electrode material such as indium oxide or zinc oxide to which indium is added, and light may be extracted from the cathode side. In that case, the light extraction surface side of the high refractive index layer and the translucent body is the cathode side.

(2) Electroluminescence layer The electroluminescence layer 2 is formed by a material that exhibits a light emission phenomenon when an electric field is applied. The electroluminescence layer 2 may have a single layer structure or a functionally separated multilayer structure. Good. In the case of a multilayer structure, examples of the layer that may be included include a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer. As a material used for the electroluminescence layer, a conventionally used electroluminescence material can be used. For example, activated zinc oxide ZnS: X (where X is an activating element such as Mn, Tb, Cu, Sm), CaS: Eu, SrS: Ce, SrGa ₂ S ₄ : Ce, CaGa ₂ S ₄ : Ce, CaS: Pb, BaAl ₂ S ₄ : Eumberly used inorganic electroluminescent materials, 8-hydroxyquinoline aluminum complexes, aromatic amines, anthracene single crystals, etc. Conjugated polymers such as electroluminescent materials, poly (p-phenylene vinylene), poly [2-methoxy-5- (2-ethylhexyloxy) -1,4-phenylene vinylene], poly (3-alkylthiophene), polyvinyl carbazole Examples thereof include, but are not limited to, organic electroluminescent materials. In addition to these light-emitting compounds, materials capable of phosphorescence emission from a triplet state or compounds derived from these fluorescent dyes can also be used.

  The thickness of the electroluminescent layer 2 is usually 10 nm or more, preferably 30 nm or more, more preferably 50 nm or more, and usually 1000 nm or less, preferably 500 nm or less, more preferably 200 nm or less.

  The electroluminescence layer 2 can be formed by a vacuum film formation process such as vapor deposition or sputtering, or a coating process using chloroform or the like as a solvent.

(3) High Refractive Index Layer The high refractive index layer 3 referred to in the present invention is provided for taking out guided light traveling in the plane direction inside the thin film including the electroluminescent layer 2, and the refractive index is usually 1.55 or more. Preferably, it refers to a layer of 1.6 or more, more preferably 1.7 or more, most preferably 1.9 or more, particularly preferably 2.0 or more, usually 2.5 or less, preferably 2.2 or less. The high refractive index layer may be formed from a plurality of layers, in which case the refractive index indicates the average value of the layers. In addition, the refractive index in this invention says what was measured with the spectroscopic ellipsometer (wavelength range: 350-900 nm). However, a prism coupler is used when measurement and analysis are difficult depending on the sample.

  The high refractive index layer 3 has at least a transparent electrode layer 3A. The high refractive index layer 3 may be composed of one layer of the transparent electrode layer 3A, and as shown in FIG. 1, the transparent electrode layer 3A and the intermediate layer 3B having the same refractive index are combined. It may be a layer.

  In the present invention, since the guided light in the thin film including the electroluminescence layer 2 is also moved into the high refractive index layer 3, the high refractive index layer 3 has a refractive index equivalent to that of the transparent electrode layer 3A and the transparent electrode 3A. It is preferably a layer composed of the intermediate layer 3B. In the present specification, “refractive index is equivalent” means that the difference between one refractive index and the other refractive index is less than 0.3, preferably 0.2 or less, particularly preferably 0.1 or less, Preferably it means 0.02 or less.

  The thickness of the high refractive index layer 3 is usually 200 nm or more, preferably 600 nm or more, and is usually 100 μm or less, preferably 50 μm or less, more preferably 10 μm or less. If the thickness is less than 200 nm, it is difficult to control the interface between the transparent electrode layer 3A and the intermediate layer 3B, which may cause a black spot at the time of light emission and a decrease in the lifetime. Therefore, the high refractive index layer 3 only needs to have a film thickness sufficient to obtain suitable surface smoothness as described below.

  The surface (transparent electrode layer side surface) of the high refractive index layer is preferably smooth, and the surface roughness Ra is preferably 80 nm or less, more preferably 50 nm or less, and even more preferably 30 nm or less. If the surface roughness Ra exceeds 80 nm, there is a possibility of causing a black spot or a reduction in the lifetime during electroluminescence emission. However, it is difficult to form a surface property having a surface roughness Ra smaller than 0.1. Therefore, the surface roughness Ra is preferably 0.1 nm or more. The surface roughness Ra of the high refractive index layer 3 can be confirmed by a contact type step / surface roughness / fine shape measuring apparatus (KLB Tencor Corporation).

<1> Transparent electrode layer The transparent electrode layer 3A normally functions as an anode of an electroluminescence element. As the transparent electrode layer 3A, indium oxide to which tin is added (commonly referred to as ITO), zinc oxide to which aluminum is added (commonly referred to as AZO), zinc oxide to which indium is added (commonly referred to as IZO) A complex oxide thin film is preferably used. In particular, ITO is preferable.

  In the case of a transparent electrode layer that does not directly form the light scattering function described later, the parallel light transmittance in the visible light wavelength region is preferably as large as possible, usually 50% or more, preferably 60% or more, more preferably 70% or more. is there.

The electrical resistance of the transparent electrode layer 3A is preferably as small as the sheet resistance value, but is usually 1 to 100Ω / □ (= 1 cm ² ), and the upper limit is preferably 70Ω / □, and more preferably 50Ω / □. It is.

  The thickness of the transparent electrode layer 3A is usually 0.01 to 10 μm as long as the above-described light transmittance and surface resistance value are satisfied. However, from the viewpoint of conductivity, 0.03 μm or more is preferable, and 0.05 μm. The above is more preferable. On the other hand, from the viewpoint of light transmittance, it is preferably 1 μm or less, more preferably 0.5 μm or less.

  As a coating solution composition for forming the transparent electrode layer 3A, for example, ITO fine particles dispersed in an organic solvent together with a conductive polymer or other resin binder, or a conductive polymer material can be used. Not. The transparent electrode layer 3A is formed into a pattern necessary as an electrode of an electroluminescent element by photolithography, ink jet, or the like using this coating solution. The line width after patterning is typically about 1 to 10 μm, but is not limited thereto.

<2> An intermediate layer having a refractive index equivalent to that of the transparent electrode layer (hereinafter referred to as an intermediate layer)
As shown in FIG. 1, the intermediate layer 3B may be provided on the light extraction surface side or the electroluminescent layer 2 side with respect to the transparent electrode layer 3A. Or you may provide in both of these. When the intermediate layer 3B is provided on the light extraction surface side of the transparent electrode layer 3A, the intermediate layer 3B preferably has an insulating property, and when the intermediate layer 3B is provided on the electroluminescence layer 2 side, it may have conductivity. preferable. However, as shown in FIG. 1, it is more preferable to provide the insulating intermediate layer 3B on the light extraction surface side of the transparent electrode layer 3A.

As the intermediate layer 3B, a film formed by a sol-gel reaction or a film formed by a vacuum process is used, and the material thereof is SiN _x O _y (x and y are arbitrary numbers of 0 or more, respectively), TiO ₂ , ZrO _2. Inorganic oxide materials such as zeolite, thermosetting resins, UV curable resins, organic materials such as conductive resins, or composite materials thereof. The intermediate layer 3B may be a laminate of these materials. The material of the intermediate layer 3B is not particularly limited, but since it is important that the refractive index is the same as that of the transparent electrode layer 3A, TiO ₂ , Al ₂ O ₃ , ZrO ₂ , Ta ₂ are contained in a matrix such as resin or silicate. The refractive index may be adjusted by dispersing high refractive index fine particles such as O ₃ . These fine particles may be used alone or in combination of two or more. Here, specific examples of the resin constituting the matrix include polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polystyrene, polyethersulfone, polyarylate, polycarbonate resin, polyurethane, acrylic resin, polyacrylonitrile, polyvinyl acetal, polyamide. , Polyimide, diacrylphthalate resin, cellulosic resin, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, other thermoplastic resins, and copolymers of two or more monomers constituting these resins It is done.

  It is important for the intermediate layer 3B to have a refractive index close to that of the transparent electrode layer 3A. If the refractive index difference is 0.3 or more, the guided light in the thin film including the electroluminescent layer 2 cannot be sufficiently extracted. It is important that the difference in refractive index between the transparent electrode layer 3A and the intermediate layer 3B is less than 0.3, preferably 0.2 or less, particularly preferably 0.1 or less, and particularly preferably 0.02 or less. is there.

  The thickness of the intermediate layer 3B is usually 250 nm or more, preferably 600 nm or more, and usually 50 μm or less, preferably 10 μm or less.

  The intermediate layer 3B can be usually formed by a coating process such as spin coating, dip coating, or die coating, or a vacuum process such as vapor deposition or sputtering.

  The surface of the intermediate layer 3B is preferably smooth, and the surface roughness Ra is preferably 100 nm or less, more preferably 50 nm or less, and even more preferably 10 nm or less. If the surface roughness exceeds 100 nm, there is a possibility of causing black spots or a reduction in life during electroluminescence emission. However, since it is difficult to form the intermediate layer 3B with surface roughness Ra = 0.05 nm or less, the surface roughness Ra of the intermediate layer 3B is usually 0.05 nm or more. The surface roughness Ra of the intermediate layer 3B can be confirmed by a contact type step / surface roughness / fine shape measuring device (KLB Tencor).

<3> Gas Barrier Layer In the present invention, particularly when the high refractive index layer 3 includes the transparent electrode layer 3A and the intermediate layer 3B having the same refractive index as the transparent electrode layer 3A, the high refractive index of the intermediate layer 3B or the like. Part or all of the layer 3 has a chemical adverse effect on the transparent electrode layer 3A, and there is a risk of black spots occurring during electroluminescence emission and a reduction in life, so that there is a risk between the transparent electrode layer 3A and the intermediate layer 3B. It is preferable to have a gas barrier layer.

As a material for forming the gas barrier layer, ZrC ₂ , TiO ₂ , Al ₂ O ₃ , CeO ₂ , TiN, Ta ₂ O ₅ , SiO _x N _y , SiN, SiO _x , SnO ₂ , Sb ₂ O ₅ , Y ₂ O ₃ , La ₂ O ₃ , In ₂ O _{3 and the} like, or a mixture thereof, but these are not limited, and any of them can be used as long as it is visible and has no absorption or at least a dense film structure, particularly an inorganic compound. Is preferably the main component.

  The thickness of the gas barrier layer is not particularly limited, but considering barrier properties, it is usually 5 nm or more, preferably 20 nm or more, more preferably 50 nm or more, particularly preferably 100 nm or more, usually 10 μm or less, preferably 1 μm or less, particularly Preferably it is 400 nm or less. For example, it is preferable to provide a gas barrier layer containing an inorganic material of 5 nm to 400 nm, preferably 10 nm to 300 nm, specifically about 30 nm.

This gas barrier layer is formed by a vacuum process such as vapor deposition or sputtering. The refractive index of the gas barrier layer is preferably equal to that of the transparent electrode layer 3A, but a low refractive index material can be used as long as the film thickness is 200 nm or less. Examples of the low refractive index material in this case include fluoride compounds such as MgF ₂ , NaF ₂ , and NaF ₂ , and nanoporous materials.

(4) Translucent body The translucent body 4 is usually a substrate of an electroluminescence element.

  The light-transmitting body 4 is preferably the same as or higher than the refractive index of the high refractive index layer 3, but the refractive index is usually 1.4 or higher, preferably 1.45 or higher, more preferably 1. 47 or more, usually less than 1.9, preferably less than 1.80, more preferably less than 1.75. The refractive index of the translucent body 4 is measured by an optical method such as ellipsometer, reflectance measurement, prism coupler, etc., but is not particularly limited.

As the transparent body 4 having such a refractive index, a transparent substrate made of a general-purpose material can be used. For example, various types of shot glass such as BK ₇ , SF ₁₁ , LaSFN ₉ , BaK ₁ , F ₂ , synthetic phased silica glass, optical crown glass, low expansion borosilicate glass, sapphire glass, soda glass, alkali-free glass, etc. Acrylic resins such as polymethyl methacrylate and cross-linked acrylate, aromatic polycarbonate resins such as bisphenol A polycarbonate, polyester resins such as polyethylene terephthalate, amorphous polyolefin resins such as polycycloolefin, epoxy resins, styrene resins such as polystyrene, poly Polysulfone resins such as ether sulfone, synthetic resins such as polyetherimide resin, and the like may be mentioned, and a laminate of these may also be used. Of these, shot glass, synthetic phased silica glass, optical crown glass, low expansion borosilicate glass, soda glass, alkali-free glass, acrylic resin, aromatic polycarbonate resin, and polysulfone resin are preferable.

  In addition, on the light extraction side (the light extraction surface side of a layer having a light scattering function to be described later) of these translucent bodies 4, an antireflection film, a circularly polarizing film, a retardation film, etc. are used depending on the purpose and application. An optical film may be formed or bonded.

  The thickness of the translucent body 4 is usually 0.1 mm or more and 10 mm or less. The thickness is preferably 0.2 mm or more from the viewpoint of mechanical strength and gas barrier properties, and is usually 5 mm or less, preferably 3 mm or less from the viewpoint of weight reduction and light transmittance.

  Although the transparent body 4 is preferably a transparent substrate, it may be a top emission type element in which a protective cover is provided on the high refractive index layer instead of this substrate. In this case, the transparent body 4 is a protective cover. It is preferable to become. The material of the protective cover is not particularly limited as long as it is transparent, and examples thereof include various resin materials such as a curable resin and coating materials such as a sol-gel film.

(5) Layer having Light Scattering Function The present invention is characterized by having layers 5A and 5B having a light scattering function on the light extraction surface side of the high refractive index layer 3 and the light transmitting body 4, respectively.

  Here, the light scattering function refers to multiple scattering of emitted light by Mie scattering. With this light scattering function, the guided light in the thin film including the electroluminescence layer 2 or the light that has leaked out of the guided light can be scattered in the light extraction direction. In order to efficiently perform multiple scattering, it is necessary to optimally adjust the refractive index difference between the scatterer or scattering shape and the matrix around the scatterer or scattering shape and the size of the scatterer or scattering shape. For example, the distance between the scatterers is preferably equal to or less than the scatterer size, and more preferably ½ or less of the scatterer size. Moreover, it is preferable that the distance between scatterers is 1/10 or more of a wavelength. These sizes can be confirmed by cross-sectional observation with a scanning electron microscope or transmission electron microscope, or by X-ray scattering measurement.

  Here, the scatterer refers to the following transparent particles, the scattering shape refers to the shape of the uneven surface, the matrix specifically, in the case of a layer containing transparent particles, This refers to the same matrix as that described in the intermediate layer 3B. In the case of an uneven structure interface, it refers to the material of adjacent layers, air, and the like.

The light extraction surface side of each of the high refractive index layer 3 and the translucent body 4 is normally refracted as an interface between the high refractive index layer 3 and the translucent body 4 and an interface between the translucent body 4 and air. In many cases, the rate difference increases.
In particular, the layer 5B having a light scattering function provided on the light extraction surface side of the translucent body 4 is preferably higher than the refractive index of the translucent body 4 in terms of efficiently extracting the substrate mode. The refractive index difference between the refractive index of the translucent body 4 and the layer 5B having a light scattering function is preferably about 0.02 or more and about 1.5 or less.

  The layers 5A and 5B having the light scattering function may be formed by forming different layers from the high refractive index layer 3 and the transparent body 4, or the high refractive index layer 3 or the transparent body. Although the surface of each layer 4 may have a concavo-convex surface by polishing such as blasting, a layer containing an irregular uneven structure interface or transparent particles is particularly preferable.

  The thickness in the film thickness direction of the layers 5A and 5B having the light scattering function is usually preferably 100 nm or more, and more preferably 200 nm or more. If the thickness is less than 100 nm, the multiple scattering property is lowered, and the anisotropy of scattering is increased, so that the viewing angle dependency of luminance may appear. Further, the thickness of the layers 5A and 5B having a light scattering function is preferably 50 μm or less, and more preferably 10 μm or less. If the thickness exceeds 50 μm, the scattering characteristics change due to the optical path of the emitted light through the layer having the light scattering function, and there is a risk that the viewing angle dependency of luminance appears as described above.

  The light scattering function of the layers 5A and 5B having a light scattering function is usually preferably 90% or less, more preferably 80% or less, and further preferably 70% or less in terms of light transmittance. Further, considering the loss of emitted light due to multiple scattering, it is usually preferably 25% or more, more preferably 40% or more. For example, in D65 light, the parallel light transmittance of each of the layers 5A and 5B having the light scattering function is preferably 30% or more and 80% or less.

<1> Layer having a light scattering function composed of an irregular uneven structure interface Here, the irregular uneven interface means an aperiodic uneven structure interface, and the emitted light reduces total reflection at the interface. For this reason, the surface roughness Ra is preferably 10 nm or more, and more preferably 100 nm or more. Moreover, 10 micrometers or less are preferable from a viewpoint of light emission bleeding, and 1 micrometer or less is more preferable. Conventionally, an advanced rough surface structure including a photonic crystal microlens has been proposed, but it is important that the uneven structure is irregular not only in terms of cost but also in terms of scattering anisotropy. This surface roughness Ra is measured several times under the condition of one scanning distance of 0.5 μm using a P-15 type contact surface roughness meter manufactured by KLA-Tencor based on the standard defined in JIS B0601: 2001. It is obtained by calculating a measured average value.

  The irregular uneven structure interface as a layer having a light scattering function can be formed by polishing treatment such as blasting, but can also be formed by applying transparent particles to the interface.

<2> Layer having a light scattering function comprising a layer containing transparent particles Here, the transparent particles are particles having no or little absorption in the visible light region (the absorption is usually 30% or less). TiO ₂ , SiO ₂ , ZrO ₂ , Al ₂ O ₃ , Ta ₂ O ₃ , ZnO ₂ , Sb ₂ O ₃ , ZrSiO ₄ , zeolite or porous materials thereof, inorganic particles or acrylic resins based on them, Organic particles such as styrene resin and polyethylene terephthalate resin can be used. In particular, inorganic particles are preferable, and among them, those composed of TiO ₂ , SiO ₂ , porous SiO ₂ , ZrO ₂ , Al ₂ O ₃ , and zeolite are preferable. Moreover, only 1 type may be used for transparent particle | grains and 2 or more types may be used for it.

  Usually, in order to cause effective Mie scattering, the particle size is 100 nm or more, preferably 250 nm or more, more preferably 300 nm or more, and usually 20 μm or less, more preferably 10 μm or less.

  In particular, in the layer 5A having a light scattering function, the particle size is preferably 80 to 700 nm, and in the layer 5B having a light scattering function, the particle size is preferably 150 nm to 8 μm.

  Further, the refractive index difference between the matrix and the transparent particles as the scatterer is usually preferably 0.01 or more, more preferably 0.03 or more, more preferably 0.05 or more, and the upper limit is preferably less than 2. More preferably, it is less than 1.5, More preferably, it is less than 1. If this refractive index difference is too low, it will be difficult to obtain effective Mie scattering, and if the refractive index difference is too large, backscattering will increase, and a sufficient light extraction rate may not be obtained.

In order to extract the thin film mode, the difference ΔN (= N _m −N _s ) between the refractive index (N _m ) of the matrix and the refractive index (N _s ) of the transparent particles as the scatterer is −1.8 to −0.3. It is preferable that Furthermore, the refractive index (N _s ) of the scatterer is preferably 1.8 or more. On the other hand, in order to take out the substrate mode, it is preferable that the refractive index difference ΔN between the matrix and the scatterer is −0.3 to 1.5. Further, the refractive index (N _s ) of the scatterer is preferably 1.7 or less.

  In the present invention, the refractive index of the transparent particles which are scatterers contained in the layer 5A having the light scattering function on the light extraction surface side of the high refractive index layer 3 is 1.6 or more, preferably 1.8 or more. In addition, the refractive index of the transparent particles, which are the scatterers included in the layer 5B having the light scattering function on the light extraction surface side of the translucent body 4, is preferably 1.7 or less, and more preferably 1.57 or less. Is preferred. This is because the transparent particles preferably have different scattering characteristics.

  Two or more kinds of transparent particles having different materials or different particle sizes may be used in combination. Further, the layer having a light scattering function composed of a layer containing transparent particles may be a laminated film using different transparent particles and / or matrices.

  The layer containing transparent particles is usually a light multiple scattering layer formed by applying a coating liquid in which transparent particles are dispersed in a matrix precursor.

As described above, the difference in refractive index between the matrix and the transparent particles is usually preferably 0.01 or more, more preferably 0.03 or more, more preferably 0.05 or more, and the upper limit is preferably less than 2. More preferably, it is less than 1.5, more preferably less than 1, and in order to take out the thin film mode, the difference ΔN (= N _m −N _s ) between the refractive index of the matrix and the refractive index of the transparent particles is −1. It is preferable that the refractive index difference ΔN between the matrix and the scatterer is −0.3 to 1.5 in order to take out the substrate mode. Although it can be changed by the transparent particles to be dispersed, as a general-purpose material, for example, a sol-gel precursor such as a silicate oligomer, a reactive precursor such as a monomer of a thermosetting resin or a UV curable resin, The melt of the resin, or precursor can be cited as a main component thereof.

  The transparent particle content in the coating solution needs to be adjusted so that Mie scattering is multiple-scattered in the layer containing the formed transparent particles.

  Examples of the coating method of the coating liquid include spin coating, dip coating, die coating, casting, spray coating, and gravure coating. Of these means, spin coating, dip coating, and die coating are preferred from the viewpoint of film uniformity.

  Other than <1> and <2>, since it is important in the present invention to reduce the total reflection of the emitted light rays at the uneven structure interface, the uneven structure is an irregular uneven structure interface due to a difference in refractive index. There may be.

(6) Other Layers In the present invention, in order to more efficiently take out the emitted light beam transferred to the high refractive index layer 3 from the translucent body 4, a transparent material is interposed between the high refractive index layer 3 and the translucent body 4. A layer having a refractive index lower than that of the light body 4 (hereinafter referred to as a low refractive index layer) is preferably provided. By providing the low refractive index layer, directivity can be imparted to extracted light.

  When a low refractive index layer is provided, the low refractive index layer has a refractive index of usually 1.05 or more, particularly 1.1 or more, usually 1.5 or less, preferably 1.35 or less, particularly preferably 1.3. The following layers containing a fluoride resin such as silica and cyclic Teflon, magnesium fluoride, and the like are preferable, but a layer containing porous silica is particularly preferable. It is important that the refractive index of the low refractive index layer is lower than that of the transparent body. However, if it is too low, a problem is likely to occur in the mechanical strength, and if it is high, the light extraction efficiency decreases. Moreover, you may introduce | transduce into a silica an organic component for the purpose of hydrophobization, a softness | flexibility provision, crack prevention, etc. as needed. For the top emission type, there is no problem in the device configuration even if the low refractive index layer is air (void). In this case, the refractive index is 1.0.

[Configuration of lighting device]
The illumination device of the present invention uses the electroluminescence element of the present invention as described above as a light source.

  That is, the electroluminescence element of the present invention can suppress the reduction in luminance at the pixel end, can impart directivity to the extracted light, and can obtain uniform light emission as illumination. And is useful as a light source of a lighting device.

  The illuminating device of the present invention is formed by arranging pixels made of a plurality of electroluminescent elements on the front surface of an object to be illuminated. In particular, it is preferably used as planar illumination.

  EXAMPLES Next, although an Example demonstrates this invention more specifically, this invention is not limited to a following example, unless the summary is exceeded.

<Reference Example 1>
On the opposite side of the light extraction surface of Asahi Glass Co., Ltd. alkali-free glass (refractive index 1.5), ITO is sputtered at room temperature to a film thickness of about 100 nm to form a transparent electrode layer. After forming the transport layer, a tris (8-hydroxyquinolinate) aluminum complex is deposited with a film thickness of about 150 nm to form a light emitting layer. Thereafter, Al is deposited on the light emitting layer to a thickness of about 100 nm to form an organic electroluminescence element.

  The number of black spots with a diameter of 0.5 mm or more when the electroluminescence element emits light is about 3 or less in a 5 cm square.

<Example 1>
Silica particles SO-G2 (average particle size: 600 nm, refractive index: 1.5) manufactured by Admatechs Co., Ltd. as silicate oligomer (oligomer) on the light extraction surface of non-alkali glass manufactured by Asahi Glass Co., Ltd. as a translucent body (substrate). A precursor coating solution dispersed at a refractive index of 1.5) after curing is spin-coated and cured at 250 ° C. to form a layer having a light scattering function. The surface roughness Ra of the layer having the light scattering function is about 200 nm, and the light transmittance is about 50%.

  A porous silica film is formed on the other surface of the glass substrate by a casting method to form a low refractive index layer. This porous silica film has a film thickness of about 830 nm and a refractive index of about 1.2 from a spectroscopic ellipsometer.

  A precursor coating solution in which zirconia particles RC-100 (average particle size 1.9 μm, refractive index 2.0) manufactured by Daiichi Rare Element Chemical Industry Co., Ltd. is dispersed in a silicate oligomer is spin-coated on this porous silica film. And a layer having a light scattering function by curing at 250 ° C. The surface roughness Ra of the layer having the light scattering function is about 350 nm, and the light transmittance is 50% (only in the layer having the light scattering function).

  Furthermore, UV curable resin UV1000 monomer manufactured by Mitsubishi Chemical Co., Ltd. in which titania particles TTO-55D manufactured by Ishihara Sangyo Co., Ltd. (average particle size 30 nm, refractive index 2.4) are dispersed on the surface on the transparent electrode layer side. Refractive index 1.6) After spin-coating the coating solution, UV curing is performed to form a high refractive index layer. Due to the prism coupler, the titania particle composite UV curable resin layer has a refractive index of about 1.8, a film thickness of about 10 μm, and a surface roughness Ra of about 1 nm.

  On this titania particle composite UV curable resin layer, ITO is sputtered at a room temperature with a film thickness of about 100 nm, a transparent electrode layer is formed, a hole injection layer and a hole transport layer are further formed, and tris (8-hydroxy) is formed thereon. Quinolinato) An aluminum complex is deposited with a film thickness of about 150 nm to form a light emitting layer. Thereafter, Al is deposited on the light emitting layer to a thickness of about 100 nm to form an organic electroluminescence element.

  The initial luminance of the obtained organic electroluminescence device is about 2.5 times as high as that of Reference Example 1. In addition, the number of black spots having a diameter of 0.5 mm or more during light emission is about 5 or less in a 5 cm square.

<Example 2>
Dip coat a precursor coating solution in which silica particles SO-G2 (average particle size 600 nm) manufactured by Admatechs Co., Ltd. are dispersed in a silicate oligomer on both surfaces of non-alkali glass manufactured by Asahi Glass Co., Ltd. as a translucent body (transparent substrate). And cured at 250 ° C. to form a layer having a light scattering function. The surface roughness Ra of the layer having the light scattering function and the light transmittance only on one side are considered to be the same as those in Example 1.

  A UV curable resin UV1000 monomer coating solution manufactured by Mitsubishi Chemical Co., Ltd., in which titania particles TTO-55D (average particle size 30 nm) manufactured by Ishihara Sangyo Co., Ltd. are dispersed, is spin-coated on the surface to be the transparent electrode layer side, and cured. A high refractive index layer is used. Due to the prism coupler, this titania particle composite UV curable resin layer has a refractive index of about 1.8, a film thickness of about 7 μm, and a surface roughness Ra of about 2 nm.

  On this titania particle composite UV curable resin layer, ITO is sputtered at room temperature to a thickness of about 100 nm to form a transparent electrode layer, and further, a hole injection layer and a hole transport layer are formed, and tris (8-hydroxy) is formed thereon. Quinolinato) An aluminum complex is deposited with a film thickness of about 150 nm to form a light emitting layer. Thereafter, Al is deposited on the light emitting layer to a thickness of about 100 nm to form an organic electroluminescence element.

  The initial luminance of the obtained organic electroluminescence element is about 1.8 times as high as that of Reference Example 1.

<Example 3>
In Example 1, instead of the precursor coating liquid in which zirconia particles are dispersed in a silicate oligomer on a porous silica film, Titania particles TS-01 (average particle size 215 nm, refractive index 2.6) manufactured by Showa Denko K.K. ) And Ishihara Sangyo Co., Ltd. titania particles TTO-55D (average particle size 30 nm) in a UV coating resin UV1000 monomer coating solution made by Mitsubishi Chemical Co., Ltd. A layer having a light scattering function is formed. Due to the prism coupler, this titania particle composite UV curable resin layer has a refractive index of about 1.8, a film thickness of about 6 μm, and a surface roughness Ra of about 1 nm. The light transmittance is about 70% (only with a layer having a light scattering function).

  On this titania particle composite UV curable resin layer, ITO is sputtered at room temperature to a thickness of about 100 nm to form a transparent electrode layer, and further, a hole injection layer and a hole transport layer are formed, and tris (8-hydroxy) is formed thereon. Quinolinato) An aluminum complex is deposited with a film thickness of about 150 nm to form a light emitting layer. Thereafter, Al is deposited on the light emitting layer to a thickness of about 100 nm to form an organic electroluminescence element.

  The initial luminance of the obtained organic electroluminescence device is about 2.3 times as high as that of Reference Example 1. In addition, the number of black spots having a diameter of 0.5 mm or more during light emission is about 5 or less in a 5 cm square.

<Reference Example 2>
On the opposite side of the light extraction surface of non-alkali glass (translucent material) manufactured by Asahi Glass Co., Ltd., ITO was sputtered at room temperature with a film thickness of 130 nm to form a transparent electrode layer. Furthermore, after forming a coating type hole injection layer with a film thickness of 30 nm and a hole transport layer (PPD: p-phenylenediamine) with a film thickness of 45 nm on this transparent electrode layer, tris (8-hydroxyquinolinate) was formed. An electroluminescent layer was formed by vapor-depositing an aluminum complex with a film thickness of 60 nm to form a light emitting layer. Then, LiF and Al were vapor-deposited with the film thickness of 0.5 nm and 80 nm as an electrode (cathode) on the electroluminescent layer, respectively, and the organic electroluminescent element was formed.

  The light extraction rate of this element is set to 1 for the elements of Examples 4 to 7 and Comparative Examples 1 and 2 below.

<Example 4> Fabrication of an element having a concavo-convex structure on a translucent surface and a transparent particle-containing layer on the back surface The light extraction surface side of non-alkali glass (translucent material) manufactured by Asahi Glass Co., Ltd. is blasted Thus, a concavo-convex structure was formed on the surface to form a layer having a light scattering function. The surface roughness Ra of this blasted surface was 560 nm, and the parallel light transmittance was 10%.

  Next, on the side (electroluminescence layer) opposite to the blasted surface of the glass substrate, Rutile type titania particles R-61N (average dispersion particle size 250 nm, refractive index 2.6) manufactured by Sakai Chemical Industry Co., Ltd. A precursor coating solution dispersed in a UV coating resin UV1000 monomer coating solution manufactured by Co., Ltd. was spin-coated and then UV-cured to form a layer having a light scattering function. The layer having the light scattering function has a film thickness of 3.5 μm, a refractive index of 1.62, a surface roughness Ra of 1.5 nm, and a parallel light transmittance of 56%.

  Thus, an electroluminescence element was formed in the same manner as in Reference Example 2 except that layers having a light scattering function were formed on both surfaces of the glass substrate.

  The initial luminance of the obtained organic electroluminescence element is 0 in comparison with that in Reference Example 2 when the measurement range is 1 mm square (evaluation condition 1) and 10 mm square (evaluation condition 2) with respect to the light emitting area of 5 mm square. The light extraction rates were .96 times (evaluation condition 1) and 1.34 times (evaluation condition 2), and the luminance reduction at the edge of the element was suppressed, and the overall luminance was also improved.

<Example 5> Fabrication of elements having transparent particle-containing layers on both surfaces of a light-transmitting body On the light extraction surface of non-alkali glass manufactured by Asahi Glass Co., Ltd., silica particles SO-G5 (average dispersed particles) manufactured by Admatex Co., Ltd. A precursor coating solution having a diameter of 530 nm) dispersed in a silicate oligomer was dip-coated and cured at 150 ° C. for 15 minutes and further at 250 ° C. for 15 minutes to form a layer having a light scattering function. The layer having the light scattering function had a surface roughness Ra of 355 nm and a parallel light transmittance of 54%.

  Next, on the opposite side (electroluminescence layer) of this glass substrate, Rutile-type titania particles R-61N (average dispersion particle size 250 nm, refractive index 2.6) manufactured by Sakai Chemical Industry Co., Ltd. are UV cured by Mitsubishi Chemical Corporation. The precursor coating solution dispersed in the resin UV1000 monomer coating solution was spin-coated and then UV-cured to form a layer having a light scattering function. The layer having the light scattering function had a film thickness of 3.5 μm, a refractive index of 1.62, a surface roughness Ra of 1.5 nm, and a parallel light transmittance of 56%.

  Thus, an electroluminescence element was formed in the same manner as in Reference Example 2 except that layers having a light scattering function were formed on both surfaces of the glass substrate.

  The initial luminance of the obtained organic electroluminescence element is 0 in comparison with that in Reference Example 2 when the measurement range is 1 mm square (evaluation condition 1) and 10 mm square (evaluation condition 2) with respect to the light emitting area of 5 mm square. The light extraction rates are .99 times (evaluation condition 1) and 1.39 times (evaluation condition 2), and a reduction in luminance at the end of the element is suppressed, and the overall luminance is also improved.

<Example 6> An element having transparent particle-containing layers on both sides of a light-transmitting body, and further having a low refractive index layer The light of the substrate of Example 5 is placed on the light extraction surface side of non-alkali glass manufactured by Asahi Glass Co., Ltd. A layer having the same light scattering function as that on the extraction surface side was formed.

  Next, a precursor solution obtained by dissolving the triblock polymer Pluronic in partially hydrolyzed alkoxysilane was applied to the opposite side of the substrate and baked at 450 ° C. to form a porous silica layer. This porous silica film had a refractive index of 1.15 at a film thickness of 830 nm and a wavelength of 550 nm from a spectroscopic ellipsometer, and this was used as a low refractive index layer.

  Furthermore, a precursor coating solution in which rutile-type titania particles R-61N (average dispersion particle size 250 nm) manufactured by Sakai Chemical Industry Co., Ltd. are dispersed in a UV curable resin UV1000 monomer coating solution manufactured by Mitsubishi Chemical Corporation on the low refractive index layer. Was spin-coated and UV cured to form a layer having a light scattering function. The layer having the light scattering function has a film thickness of 3.5 μm, a refractive index of 1.62, a surface roughness Ra of 1.5 nm, and a parallel light transmittance of 56%.

  In this way, an electroluminescence element was formed in the same manner as in Reference Example 2 except that the two transparent particle-containing layers and the low refractive index layer were formed.

The initial luminance of the obtained organic electroluminescence device is 1 in comparison with that in Reference Example 2 when the measurement range is 1 mm square (evaluation condition 1) and 10 mm square (evaluation condition 2) with respect to the light emitting area 5 mm square. The light extraction rates were .22 times (evaluation condition 1) and 1.39 times (evaluation condition 2).
In this element, by combining the low refractive index layer, it was possible to achieve both high luminance and directivity of the extracted light toward the front.

<Example 7> Element having transparent particle-containing layers on both surfaces of a light-transmitting body, and further having a low refractive index layer Asahi Glass Co., Ltd., alkali-free glass light extraction surface, Admatex Co., Ltd. silica particles A precursor coating solution in which SO-G5 (average dispersion particle size of 408 nm) was dispersed in a UV coating resin UV1000 monomer coating solution manufactured by Mitsubishi Chemical Corporation was spin-coated and UV cured to form a layer having a light scattering function. . The surface roughness Ra of the layer having the light scattering function was 61 nm, and the parallel light transmittance was 54%.

  Next, a precursor solution obtained by dissolving the triblock polymer Pluronic in partially hydrolyzed alkoxysilane was applied to the opposite side of the substrate and baked at 450 ° C. to form a porous silica layer. This porous silica film had a refractive index of 1.15 at a film thickness of 830 nm and a wavelength of 550 nm from a spectroscopic ellipsometer, and this was used as a low refractive index layer.

  Furthermore, a precursor coating solution in which rutile-type titania particles R-61N (average dispersion particle size 250 nm) manufactured by Sakai Chemical Industry Co., Ltd. are dispersed in a UV curable resin UV1000 monomer coating solution manufactured by Mitsubishi Chemical Corporation on the low refractive index layer. Was spin-coated and UV cured to form a layer having a light scattering function. The layer having the light scattering function had a film thickness of 3.5 μm, a refractive index of 1.62, a surface roughness Ra of 1.5 nm, and a parallel light transmittance of 56%.

  Thus, an electroluminescence element was formed in the same manner as in Reference Example 2 except that the two transparent particle-containing layers and the low refractive index layer were formed.

  The initial luminance of the obtained organic electroluminescence device is 1 in comparison with that in Reference Example 2 when the measurement range is 1 mm square (evaluation condition 1) and 10 mm square (evaluation condition 2) with respect to the light emitting area 5 mm square. The light extraction rate was .17 times (evaluation condition 1) and 1.50 times (evaluation condition 2).

<Comparative Example 1> An element having a transparent particle-containing layer only on the light extraction surface of the light-transmitting body On the light extraction surface of the layer having a light scattering function, silica particle SO-G5 (average particle size 408 nm) manufactured by Admatechs Co., Ltd. In the same manner as in Reference Example 2, except that the precursor coating solution in which the silicate oligomer was dispersed was dip-coated and cured at 150 ° C. for 15 minutes and further at 250 ° C. for 15 minutes to form a layer having a light scattering function. An electroluminescence element was formed. The surface roughness Ra of the layer having the light scattering function was 355 nm, and the parallel light transmittance was 54%.

  The initial luminance of the obtained organic electroluminescence element is 0 in comparison with that in Reference Example 2 when the measurement range is 1 mm square (evaluation condition 1) and 10 mm square (evaluation condition 2) with respect to the light emitting area of 5 mm square. The light extraction rates were .91 times (evaluation condition 1) and 1.00 times (evaluation condition 2).

<Comparative example 2> An element having a transparent particle-containing layer only on the light extraction surface of the high refractive index layer On the electroluminescence layer side of the alkali-free glass manufactured by Asahi Glass Co., Ltd. Rutile type titania particles R-61N manufactured by Sakai Chemical Industry Co., Ltd. Except that a precursor coating solution in which (average dispersed particle size 250 nm) was dispersed in a UV curable resin UV1000 monomer coating solution manufactured by Mitsubishi Chemical Corporation was spin coated and UV cured to form a layer having a light scattering function. An electroluminescence element was formed in the same manner as in Reference Example 2. The layer having the light scattering function had a thickness of 3.5 μm, a refractive index of 1.62, a surface roughness Ra of 1.5 nm, and a parallel light transmittance of 56%.

  The initial luminance of the obtained organic electroluminescence device is 1 in comparison with that in Reference Example 2 when the measurement range is 1 mm square (evaluation condition 1) and 10 mm square (evaluation condition 2) with respect to the light emitting area 5 mm square. The light extraction rates were 0.03 times (evaluation condition 1) and 1.31 times (evaluation condition 2). In this element, since guided light into the substrate is confined, sufficient luminance cannot be obtained, and luminance reduction at the end of the element is not sufficiently suppressed.

  The results of Examples 4 to 7 and Comparative Examples 1 and 2 are summarized in Table 1 below.

  From the above results, since the high light extraction efficiency is shown particularly in the data of the evaluation condition 2, sufficient luminance can be obtained even at the pixel end portion, and uniform light emission can be realized even if a plurality of pixels are arranged. It turns out that the electroluminescent element of invention is useful as a light source of an illuminating device. Further, it was found that the extracted light has directivity by inserting the low refractive index layer.

It is typical sectional drawing of the electroluminescent element which concerns on embodiment. It is typical sectional drawing of a common electroluminescent element.

Explanation of symbols

1 Electrode (cathode)
2 Electroluminescence layer 3 High refractive index layer 3A Transparent electrode layer (anode)
3B Intermediate layer 4 Translucent body (transparent substrate)
5A, 5B Layer with light scattering function

Claims (4)

In the electroluminescence element in which the electrode, the electroluminescence layer, the high refractive index layer, and the translucent body are arranged in this order,
On each light extraction surface side of the high refractive index layer and the translucent body, it has a layer having a light scattering function, and each of these layers having the light scattering function is a layer containing transparent particles,
Between the high refractive index layer and the translucent body, there is a layer having a lower refractive index than the translucent body, and the lower refractive index layer than the translucent body is the light on the light extraction surface side of the high refractive index layer. On the light extraction surface side of the layer having the scattering function,
In the layer having a light scattering function on the light extraction surface side of the high refractive index layer, the refractive index (N _s ) of the transparent particles is 1.8 or more, the refractive index of the matrix (N _m ) and the refractive index of the transparent particles ( N _s) the difference between the ΔN ₍₌ N m -N _s) is -0.3 from -1.8,
In the layer having a light scattering function on the light extraction surface side of the transparent body, the refractive index (N _s ) of the transparent particles is 1.5, the refractive index (N _m ) of the matrix and the refractive index (N _s ) of the transparent particles ΔN (= N _m −N _s ) is 0 to 0.1,
High refractive index layer, and an intermediate layer having a refractive index equivalent to that of transparency electrode layer and the transparent electrode layer, located on the light extraction surface side of the intermediate layer is a transparent electrode layer, is 1.55 or more refractive index An electroluminescent element characterized by being a layer of the above. The electroluminescent element according to claim 1 , wherein the refractive index of the layer having a refractive index lower than that of the translucent member is 1.3 or less. Electroluminescent device according to claim 1 or 2, characterized in that it is used as an illumination light source. An illumination device, wherein the light source is the electroluminescence element according to any one of claims 1 to 3 .

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