WO2011111629A1

WO2011111629A1 - Organic led light-emitting element and process for production thereof

Info

Publication number: WO2011111629A1
Application number: PCT/JP2011/055112
Authority: WO
Inventors: 昌也欅田
Original assignee: 旭硝子株式会社
Priority date: 2010-03-08
Filing date: 2011-03-04
Publication date: 2011-09-15
Also published as: TW201212324A

Abstract

Disclosed is an organic LED light-emitting element having reduced electric field concentration and high light extraction efficiency. Specifically disclosed is an organic LED light-emitting element comprising a light-transmitting substrate (101), a first electrode (102) which is formed on the light-transmitting substrate by a CVD technique and comprises a light-transmitting oxide film having projections and depressions on the surface thereof, a buffer layer (103) which is formed on the first electrode, an organic layer (110) which is formed on the buffer layer as a layer having light-emitting function, and a second electrode (120) which is formed on the layer having light-emitting function. The organic layer (110) may be formed so that projections and depressions are formed on the interface between the organic layer (110) and the second electrode (120), whereby multi-directional reflection can be achieved on the interface between the organic layer (110) and the second electrode (120), and the light extraction efficiency can be further improved.

Description

Organic LED light emitting device and manufacturing method thereof

The present invention relates to an organic LED (Organic Light Emitting Diode) element and a manufacturing method thereof, and more particularly to a light extraction structure of an organic LED.

The organic LED light-emitting element sandwiches a layer having a light-emitting function including a light-emitting layer made of an organic layer, applies a voltage between the electrodes, injects holes and electrons, and recombines in the organic layer, Extracts light generated in the process from the excited state to the ground state of luminescent molecules, and is used in displays, backlights, and lighting applications. The layer having a light emitting function in this specification refers to a light emitting layer, a charge injection layer such as a hole injection layer and an electron injection layer used by being stacked on the light emitting layer, and a charge transport such as a hole transport layer and an electron transport layer. All layers including the light emitting layer and the functional layer contributing to light emission of the light emitting layer are included.
The refractive index of the organic layer is about 1.8 to 2.1 at a wavelength of 430 nm. On the other hand, for example, when ITO (Indium Tin Oxide) is used as the translucent electrode layer, the refractive index differs depending on the ITO film forming conditions and composition (Sn—In ratio), but 1.9 to 2.1. The degree is common. Thus, the refractive index of the organic layer and the translucent electrode layer is close, and the emitted light reaches the interface between the translucent electrode layer and the translucent substrate without being totally reflected between the organic layer and the translucent electrode layer. . A glass substrate or a resin substrate is usually used as the translucent substrate, but the refractive index thereof is about 1.5 to 1.6, which is lower than that of the organic layer or the translucent electrode layer. Considering Snell's law, light entering the glass substrate at a shallow angle is totally reflected in the direction of the organic layer, reflected by the reflective electrode, and reaches the interface of the glass substrate again. At this time, since the incident angle to the glass substrate does not change, reflection cannot be taken out from the glass substrate by repeating reflection in the organic layer and the translucent electrode layer. As a rough estimate, it is known that about 60% of the emitted light cannot be extracted in this mode (organic layer / translucent electrode layer propagation mode). The same thing occurs at the interface between the substrate and the atmosphere. As a result, about 20% of the emitted light propagates inside the glass and light cannot be extracted (substrate propagation mode). Accordingly, the amount of light that can be extracted outside the organic LED light emitting element is less than 20% of the emitted light.

Patent Document 1 proposes a structure in which a light scattering layer, which is a translucent material layer, is provided on one side of a substrate (paragraphs 0039 to 0040). The structure which provided the light-scattering part between the board | substrate and the organic LED light emitting element is proposed by making glass particle adhere to the board | substrate surface with an acrylic adhesive, and coheringly arrange | positioning on the board | substrate surface.
Further, Patent Document 2 intends to improve the extraction efficiency, and “on a light-transmitting substrate, a resin adhesive, spray, vapor deposition, sputtering, dip, spin coating, etc., SiO ₂ particles, resin particles An organic LED light emitting device provided with a scattering layer composed of an additional layer made of a transparent material in which metal powder and metal oxide particles are dispersed (for example, paragraph 0057) is disclosed.
In Patent Document 3, there is provided a light emitting device in which a diffusion layer in which at least two kinds of fine particles having an average particle size different by one digit or more in a resin are dispersed is provided adjacent to a translucent electrode so that guided light is efficiently extracted. Disclosure.

However, Patent Documents 1 to 3 all intend to improve the scattering effect in the substrate, and do not mention improvement in light extraction efficiency due to scattering at the interface between the translucent electrode and the layer having a light emitting function. There wasn't.

In addition, the present applicant has proposed a solar cell substrate in which irregularities are formed on the surface of a transparent conductive film and the pitch of the irregularities is optimized in order to improve the photoelectric conversion efficiency of the solar cell (Patent Document 4). ).

Japanese Patent No. 2932121 Japanese Unexamined Patent Publication No. 2005-63704 Japanese Unexamined Patent Publication No. 2005-190931 Japanese Laid-Open Patent Publication No. 2002-111025

In the case of the solar cell substrate of Patent Document 4, a current flows by guiding the photoelectron pair generated in the photoelectric conversion layer toward the electrode. From the transparent conductive film to the amorphous silicon layer formed on this upper layer, The light capture efficiency is increased and the light confinement efficiency due to multiple reflection in the amorphous silicon layer is increased. Therefore, since an electric field is not applied, variation in the distance between the electrodes due to the unevenness on the surface of the transparent conductive film is not a significant problem. In addition, the wavelength of light to be used is effective in improving the light confinement efficiency in a wide band like sunlight (wavelength region 300 to 800 nm).

On the other hand, in the organic LED light emitting element, it is necessary to increase the light extraction efficiency. It is necessary to increase the light extraction efficiency by increasing the scattering effect at the interface between the transparent conductive film and the layer having a light emitting function formed thereon. Further, it is necessary to enhance the scattering effect at the interface between the layer having a light emitting function and the upper electrode formed in the upper layer, and to increase the light extraction efficiency. In addition, since a voltage is applied between the transparent conductive film sandwiching the layer having a light emitting function and the other electrode, variations in the surface of the transparent conductive film cause electric field concentration.

Here, when the surface of the transparent conductive film as the first electrode is uneven, if a layer having a light emitting function or the like is formed on the upper layer by vapor deposition or the like, the coverage of the organic layer with respect to the unevenness is deteriorated. Variations in layer thickness occur. As a result, the interelectrode distance between the first electrode and the surface of the second electrode formed on the organic layer varies. As a result, it was found that in a region where the distance between the electrodes is small, a large current flows locally in the organic layer, causing a short circuit between the electrodes and causing a non-lighting. In addition, when forming a display device composed of fine pixels, such as a high-resolution display, it is necessary to form a fine pixel pattern, and surface irregularities cause variations in pixel positions and sizes. In addition, there is a problem that the organic element is short-circuited by the unevenness.

However, as described above, in the conventional organic LED light emitting device, no consideration has been given to the behavior of light and the difference in refractive index at the interface between the transparent conductive film and the layer having a light emitting function.

This invention is made | formed in view of the said situation, and it aims at providing the organic LED light emitting element with high light extraction efficiency.
Another object of the present invention is to provide an organic LED light-emitting element with high efficiency and long life.

Accordingly, the present invention provides a light-transmitting substrate, a first electrode formed on the light-transmitting substrate by a CVD method, and formed of a light-transmitting oxide film having irregularities on the surface, and formed on the first electrode. Provided is an organic LED light emitting device comprising: a buffer layer formed; a layer having a light emitting function formed on the buffer layer; and a second electrode formed on the layer having a light emitting function.

Further, according to the present invention, in the organic LED light emitting device, the unevenness decreases in order from the surface of the first electrode to the surface of the buffer layer and the surface of the layer having the light emitting function, and the surface of the layer having the light emitting function is reduced. And those that maintain irregularities corresponding to the irregularities on the surface of the first electrode.

In the organic LED light emitting device, the surface of the buffer layer has irregularities corresponding to the irregularities of the surface of the first electrode.

In the organic LED light emitting device, the surface of the layer having the light emitting function has irregularities corresponding to the irregularities of the first electrode surface, the irregularities of the first electrode surface, and the buffer layer surface. The roughness of the surface of the layer having the light emitting function is a surface roughness that represents the degree of each unevenness in order from the surface of the first electrode to the surface of the buffer layer and the surface of the layer having the light emitting function. Including those that become smaller.

In addition, the present invention includes the organic LED light emitting device, wherein the convexity of the first electrode surface has a regular pyramid shape.

Desirably, in the organic LED light emitting device, the first electrode has a convex surface having a pyramid shape with a sharp tip.

Further, the present invention includes the organic LED light-emitting element in which the ratio of the average value H1 of the convex height to the average value W1 of the convex appearance interval on the first electrode surface is 0.5 or more.

Moreover, this invention contains the said organic LED light emitting element whose surface roughness Ra of the said buffer layer side surface of a 1st electrode is 60 nm or more.
Here, the surface roughness Ra is according to JIS B0601: 2001.

Further, the present invention includes the organic LED light emitting device, wherein the surface roughness Ra of the first electrode on the buffer layer side surface is 80 nm or more and less than 120 nm.

Further, the present invention includes the organic LED light emitting element in which the appearance interval of the convexity on the surface of the first electrode is 0.1 to 0.3 μm.

Further, the present invention includes the organic LED light emitting device, wherein the buffer layer is a solution coating type organic layer.
Here, the organic film includes a high molecular weight organic film having a molecular weight of 15000 or more and a low molecular weight organic film having a lower molecular weight. Here, the former is referred to as a polymer layer, and the latter is referred to as a low molecular layer. .

Also, in the present invention, in the organic LED light emitting device, the buffer layer is preferably a solution coating type polymer layer.

In the present invention, in the organic LED light emitting device, the buffer layer is preferably a solution coating type low molecular layer.

Further, the present invention includes the above organic LED light emitting device in which the buffer layer is a metal oxide thin film.

In the organic LED light-emitting device according to the present invention, it is desirable that the buffer layer has substantially the same surface roughness at the interface with the first electrode surface and the interface with the layer having a light emitting function.

According to the present invention, in the organic LED light emitting device, the buffer layer has a smaller surface roughness at the interface with the layer having a light emitting function than at the interface with the surface on the first electrode side. Is desirable.

Moreover, this invention contains the said organic LED light emitting element whose ratio of the average value H2 of the said convex height with respect to the average value W2 of the convex appearance space is 0.2 or more among the unevenness | corrugations of the buffer layer surface. .

In addition, the present invention includes the organic LED light-emitting element in which the ratio of the average value H3 of the height to the average value W3 of the convex appearance interval is 0.1 or more among the irregularities on the surface of the layer having a light emitting function. .

In the organic LED light emitting device, the output wavelength of the layer having a light emitting function includes a wavelength λ satisfying the following formula. (Λ <450 nm) (formula)

Further, the present invention includes the above organic LED light emitting element in which the translucent substrate is a glass substrate. Note that a translucent resin substrate may be used as the translucent substrate.

Further, the present invention includes the above organic LED light emitting element in which the translucent resin substrate is a flexible substrate.

In the organic LED light-emitting device, the first electrode includes a fluorine-doped tin oxide layer.
Further, PDOT may be used as the buffer layer and may also serve as a hole injection layer.

The present invention also includes a step of forming a first electrode made of a light-transmitting oxide film having a surface with irregularities formed on a light-transmitting substrate by a CVD method, and forming a buffer layer on the first electrode. Including a step of forming a layer having a light emitting function on the buffer layer, and a step of forming a second electrode on the layer having the light emitting function.

According to the present invention, in the method for manufacturing an organic LED light emitting device, the step of forming a layer having a light emitting function is performed on the buffer layer formed on the surface of the first electrode by forming irregularities on the surface of the first electrode. This includes a process of forming a film so as to have a step coverage of leaving the unevenness caused by the surface on the surface.

Further, in the method for manufacturing the organic LED light emitting device, the step of forming the buffer layer is unevenness corresponding to the unevenness of the surface of the first electrode, and a smaller unevenness is formed on the surface of the buffer layer. The step of forming the layer having the light emitting function is caused by unevenness on the surface of the first electrode, and is uneven corresponding to the unevenness on the surface of the buffer layer, and is about the unevenness on the surface of the buffer layer. This includes a step of forming a film so that small irregularities are formed on the surface of the layer having a light emitting function.

Further, in the method for manufacturing the organic LED light emitting element, the step of forming the buffer layer may be a step of forming the polymer layer by a coating method.

Further, in the method for manufacturing an organic LED light emitting element, the step of forming the buffer layer may be a step of forming a low molecular layer by a coating method.

Further, in the method for manufacturing an organic LED light emitting element, the step of forming the buffer layer may be a step of forming an inorganic film by a dry process.

According to the present invention, unevenness is formed at the interface between the first electrode (translucent electrode) having a buffer layer formed on the surface and the layer having a light emitting function, and light extraction efficiency is improved by scattering at this interface. Therefore, it is possible to provide a light-transmitting substrate that can provide an optical device with high extraction efficiency. In particular, the scattering effect is further enhanced by making the irregularities into pyramid-shaped irregularities having optimum dimensions.
In addition, a buffer layer can be formed over the light-transmitting electrode as the first electrode formed on the substrate, so that electric field concentration can be prevented and the light extraction efficiency can be improved due to the difference in refractive index.
Furthermore, it is possible to provide a light-transmitting substrate that has an excellent scattering effect, such as increasing the scattering effect between the light-transmitting electrode and the layer having a light-emitting function, compared to the original organic LED light-emitting element. It becomes.

Sectional drawing which shows the organic LED light emitting element of Embodiment 1 of this invention Sectional drawing which shows the board | substrate for organic LED light emitting elements of Embodiment 1 of this invention. The figure showing the photograph which shows the translucent 1st electrode surface of the board | substrate for organic LED light emitting elements of Embodiment 1 of this invention. The principal part expanded sectional schematic diagram of the translucent 1st electrode surface of the organic LED light emitting element of Embodiment 1 of this invention. The principal part expanded sectional schematic diagram of the buffer layer surface of the organic LED light emitting element of Embodiment 1 of this invention The principal part expanded sectional schematic diagram of the layer surface which has the light emission function of the organic LED light emitting element of Embodiment 1 of this invention. Sectional drawing which shows the board | substrate for organic LED light emitting elements of Embodiment 2 of this invention. Sectional drawing which shows the organic LED light emitting element of Embodiment 2 of this invention. Sectional drawing which shows the board | substrate for organic LED light emitting elements of Embodiment 3 of this invention. Sectional drawing which shows the organic LED light emitting element of Embodiment 3 of this invention.

(Embodiment 1)
Hereinafter, the organic LED light-emitting element according to Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing the structure of an organic LED light-emitting element, FIG. 2 is an enlarged cross-sectional view of the main part, FIG. 3 is a diagram showing an SEM photograph showing the first electrode surface, and FIG. FIG. 5 is a schematic cross-sectional view showing irregularities on the surface of the buffer layer, and FIG. 6 is a schematic cross-sectional view showing irregularities on the surface of the layer having a light emitting function.
In the organic LED light-emitting device of the present invention, a translucent electrode (first electrode) formed on a substrate 101 made of a glass substrate is made of tin oxide having irregularities including pyramidal projections on the surface, and is scattered. The effect is enhanced and the light extraction efficiency is improved. This first electrode is formed by CVD under controlled conditions. That is, as shown in FIG. 1, the light-transmitting substrate 100 with electrodes, a layer having a light emitting function composed of the organic layer 110, and the reflective second electrode 120 are configured. Here, the translucent substrate 100 with an electrode includes a substrate 101 made of a translucent glass substrate, a translucent first electrode 102, and a buffer layer 103. In addition, unevenness is also formed at the interface between the organic layer 110 and the second electrode 120 due to the pyramidal protrusion. Due to the unevenness, the reflection direction at the interface between the organic layer 110 and the second electrode 120 becomes multidirectional. The surface of the buffer layer 103 has unevenness corresponding to the unevenness of the surface of the first electrode 102. The surface of the organic layer 110 constituting the layer having a light emitting function has unevenness corresponding to the unevenness of the surface of the first electrode 102. Then, the unevenness on the surface of the first electrode 102, the unevenness on the surface of the buffer layer 103, and the unevenness on the surface of the organic layer 110 are sequentially changed from the surface of the first electrode 102 to the surface of the buffer layer 103 and the surface of the organic layer 110. The surface roughness representing the degree of unevenness is reduced.

The translucent substrate with an electrode 100 used in the present invention is a translucent electrode composed of a translucent glass substrate 101 and a tin oxide layer formed by a CVD method and having a pyramid-shaped projection on the surface. A first electrode 102 and a buffer layer 103 made of P-DOT / PSS (a mixture of polythiophene and polystyrene sulfonic acid) formed by a coating method are provided.

Next, the translucent first electrode 102 will be described. In the present invention, similarly to Patent Document 4, a tin oxide thin film formed using a CVD method is used.
That is, when a thin film containing tin oxide as a main component is formed using the CVD method, crystal nuclei are generated at any time and mixed into the thin film. And since the thin film which has a tin oxide as a main component is deposited while growing a crystal, each crystal nucleus grows in a radial or random one direction at any time. Therefore, crystals grown from the early stage of thin film formation and crystals generated in the later stage are mixed, and the surface unevenness of the thin film becomes non-uniform. Further, on the surface of the thin film, a dome shape, that is, a convexity with a smooth top is observed.

However, if the formation of crystal nuclei in the middle of thin film formation is suppressed, crystal growth starts selectively from the crystal nuclei generated in the initial stage of thin film formation, so that a uniform and dense projection is formed on the surface of the thin film. . In this case, the convex outer shape is a polygonal pyramid or a plateau. Therefore, it is necessary to select conditions that can increase the deposition rate so that crystal nuclei are not generated during thin film formation.

Therefore, in the formation of a thin film containing tin oxide as a main component, helium is used as a carrier gas in the CVD method to increase the crystal growth rate without generating crystal nuclei.

When helium is used as the carrier gas, it is not clear why crystal nuclei are not generated during thin film formation and why the crystal growth rate is high, but helium gas has a small molecular weight, so the molecular motion rate is low. Fast and many collisions with source gas. For this reason, the raw material gases are inhibited from reacting in the gas phase and growing into crystal nuclei. On the other hand, in the thin film forming stage, helium gas is sprayed on the substrate / thin film surface together with the raw material gas, but helium gas having a small molecular weight is selectively raised and discharged. For this reason, it is considered that the source gas is likely to accumulate near the surface of the substrate / thin film, and the crystal growth is promoted. That is, the helium gas has a function of maintaining a high concentration of the source gas near the substrate / thin film surface. Furthermore, since helium gas has extremely high chemical stability, chemical interaction does not work with the source gas, and the crystal growth of the thin film is not hindered.

As the thin film mainly composed of tin oxide, indium tin oxide doped with indium (ITO) or tin oxide thin film doped with titanium oxide, fluorine or chlorine can be used in addition to the tin oxide thin film. is there. These dope components are not particularly limited, but are required not to significantly inhibit the crystal growth of tin oxide. Thus, when different components are doped into tin oxide, new characteristics can be imparted to the thin film. For example, when titanium oxide is doped, the visible light transmittance of the thin film is increased, and when fluorine is doped, the infrared reflectance is improved.

The following can be used as the raw material gas for this thin film. For example, tin tetrachloride, monobutyltin trichloride, dimethyltin dichloride (DMT), dibutyltin dichloride, dioctyltin dichloride, and the like. Among these compounds, organotin compounds (organotin chlorides), particularly monobutyltin trichloride and dimethyltin dichloride are preferred. Further, when forming an ITO thin film, dimethylindium chloride is preferred. The source gas must contain an appropriate amount of oxygen or oxide, and for example, water vapor, carbon monoxide, nitrogen dioxide and ozone can be used as the oxide. Moreover, you may add hydrogen fluoride, chlorine, or hydrogen chloride to source gas as above-mentioned dope component.

FIG. 4 shows an enlarged view of the main part of the protrusion on the surface of the first electrode, that is, the protrusion T1. Thus, the ratio of the average value of the height H1 to the average value of the convex appearance interval W1 is 0.5. Here, the ratio of the average value of the height H1 to the average value of the convex appearance interval W1 is preferably 0.5 or more. By setting this level, film formation can be facilitated in a state where the unevenness on the electrode surface is larger than the unevenness on the surface of the buffer layer. With this configuration, the light extraction efficiency can be improved more favorably.

The surface roughness Ra of the surface of the first electrode 101 on the buffer layer 103 side is 60 nm. The surface roughness Ra of the surface on the buffer layer 103 side is desirably 60 nm or more. By setting it to this extent, film formation can be facilitated in a state where the unevenness of the electrode surface is larger than the unevenness of the buffer layer 103 surface, and this configuration can improve the light extraction efficiency more favorably.

FIG. 5 shows an enlarged cross-sectional view of the main part of the protrusion T2 on the buffer layer surface. The appearance interval W2 of the protrusion T2 on the surface of the first electrode 102 on the buffer layer 103 side is preferably 0.1 to 0.3 μm (see FIG. 5). When it exceeds 0.3 μm, the viewing angle dependency of the emitted color becomes strong. The ratio of the average value H2 of the height to the appearance interval W2 of the protrusion T2 is 0.2. This ratio is desirably 0.2 or more. With this configuration, film formation can be facilitated in a state where the unevenness of the electrode surface is larger than the unevenness of the surface of the buffer layer 103, and the light extraction efficiency can be improved more favorably.
As described above, the surface of the buffer layer 103 also forms an uneven surface, and the surface of the organic layer formed as an upper layer also forms an uneven portion.

FIG. 6 shows an enlarged view of the main part of the convex T3 on the surface of the organic layer. Thus, in the organic layer 110 constituting the layer having the light emitting function, the surface on the second electrode 120 side forms an uneven surface, and the ratio of the average value of the height H3 to the average value of the convex appearance interval W3 is It is 0.18. This ratio is desirably 0.1 or more. Since the unevenness is formed at the interface between the organic layer 110 and the second electrode 120, the reflection direction at the interface between the organic layer 110 and the second electrode 120 becomes multi-directional, and It is possible to increase light traveling toward the substrate through one electrode. Therefore, the light extraction efficiency can be improved more favorably.

According to this configuration, the first electrode 102 is formed by the CVD method so as to have irregularities on the surface, and the buffer layer 103 having irregularities reflecting the irregularities is formed on the upper layer. Therefore, the light extraction efficiency can be increased by having a scattering effect at the interface between the first electrode 101 and the buffer layer 103 and at the interface between the buffer layer 103 and the layer having a light emitting function. Further, since the unevenness is formed not on the surface of the substrate 101 but on the surface of the first electrode 110, scattering occurs at a position closer to the light emitting region, and the light extraction characteristics are further improved.

Further, the presence of the buffer layer 103 makes it possible to obtain a smooth surface while having irregularities. For this reason, for example, when forming an organic LED light-emitting element, the surface of the buffer layer 103 has little unevenness. Therefore, even when a layer having a light-emitting function is formed on the upper layer by a coating method or the like, the layer having a light-emitting function is uniform. The distance between the translucent electrode (first electrode) and the surface of the reflective electrode (second electrode) formed on the layer having a light emitting function is also uniform. . As a result, since a large voltage is not locally applied to the layer having a light emitting function, the life can be extended.

In addition, according to the present invention, when a material having a specific resistance close to that of the translucent electrode and having a large refractive index difference from the translucent electrode is selected as the buffer layer, It is possible to shift the interface and the optical interface that becomes the scattering surface. At this time, the surface of the translucent electrode (first electrode) and the reflective electrode (second electrode), which are regions where a substantial electric field is applied with solid arrows in FIG. Electrode) surface. The interval between the solid line arrows corresponds to the distance between the electrodes where the electric field is substantially applied, and the broken line arrow corresponds to the interval between the optical interfaces. Therefore, the scattering effect in the vicinity of the layer having a light emitting function can be enhanced while maintaining the distance between the electrodes of the organic LED light emitting element substantially uniform, and the light extraction efficiency can be improved and the life can be extended. it can.

Since the unevenness is formed at the interface between the organic layer 110 and the second electrode 120, the reflection direction at the interface between the organic layer 110 and the second electrode 120 becomes multi-directional, and As described above, it is possible to further increase the light directed to the substrate side through one electrode. When the surface of the first electrode, which is the base layer, has no unevenness, the unevenness is generated on the surface of the organic layer 110. As a result, regions having different thicknesses of the organic layer 110 are formed. For this reason, a variation is formed in the distance between the first electrode and the second electrode, and a large voltage is locally applied to the layer having a light emitting function, which causes a reduction in lifetime. .
On the other hand, when an independent unevenness is formed on the surface of the organic layer 110, a surface treatment such as a patterning process is required, and the interface characteristics with the second electrode formed on the upper layer are deteriorated.

Therefore, in order to form irregularities at the interface between the organic layer 110 and the second electrode 120 so that the reflection direction at the interface between the organic layer 110 and the second electrode 120 is multidirectional, the irregularities are not formed. It can be seen that the method of forming irregularities on the surface of the first electrode 102 has the most excellent method. Even when the unevenness on the surface of the organic layer 110 is smaller than the unevenness on the surface of the first electrode 102, the distance between the electrodes gently changes at the same pitch, and a large voltage is applied locally. It is possible to avoid the situation.

As described above, by forming irregularities on the surface of the first electrode 102, the interface between the first electrode and the buffer layer 103, the interface between the buffer layer 103 and the organic layer 110, the organic layer 110 and the second electrode. While repeating multi-directional reflection and refraction at each of the interfaces with 120, a long life can be maintained and light can be extracted efficiently.

Hereinafter, each member will be described in detail.
<Board>
As the light-transmitting substrate used for forming the light-transmitting substrate, a material that can withstand the temperature at which the upper functional film is formed and that has a high visible light transmittance, such as a glass substrate, is mainly used. Examples of the material of the glass substrate include inorganic glass such as alkali glass, non-alkali glass, and quartz glass. The light-transmitting substrate 101 may have a thickness of 0.1 mm to 2.0 mm, but may be thicker when the area becomes large. Further, a resin substrate may be used, and a flexible resin substrate is also applicable.

<Translucent electrode (first electrode)>
The translucent electrode (anode) is characterized by a surface shape having pyramid-shaped projections in order to enhance the scattering effect and improve the light extraction efficiency. Further, in order to extract the light generated in the layer having the light emitting function made of the organic layer 110 to the outside, 80% or more of translucency is required. In addition, a high work function is required to inject many holes. Specifically, ITO (Indium Tin Oxide), SnO ₂ , ZnO, IZO (Indium Zinc Oxide), AZO (ZnO—Al ₂ O ₃ : zinc oxide doped with aluminum), GZO (ZnO—Ga ₂ O ₃ : zinc oxide doped with gallium), Nb-doped TiO ₂ , Ta-doped TiO ₂ and other materials are used. The thickness of the light-transmitting first electrode 102 is preferably 100 nm or more. Note that the refractive index of the light-transmitting first electrode 102 is 1.9 to 2.2. Here, when the carrier concentration is increased, the refractive index of ITO can be lowered. As for the commercially available ITO, SnO ₂ : 10 wt% is standard. From this, the refractive index of ITO can be lowered by increasing the Sn concentration. However, although the carrier concentration increases with an increase in Sn concentration, there is a decrease in mobility and transmittance, so it is necessary to determine the Sn amount by balancing these.
Needless to say, the translucent electrode may be a cathode.

<Buffer layer>
As the buffer layer, in addition to an organic film such as P-DOT / PSS, inorganic materials such as refractory metal oxides such as molybdenum oxide, tungsten oxide, and vanadium oxide can be used.

<Layer having a light emitting function>
The layer having a light emitting function is an organic layer, and includes a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer. Here, either a high molecular layer or a low molecular layer can be applied. The refractive index of the organic layer is about 1.7 to 1.8.

<Hole injection layer>
The hole injection layer is required to have a small difference in ionization potential in order to lower the hole injection barrier from the translucent electrode as the first electrode. Improvement of the charge injection efficiency from the electrode interface in the hole injection layer lowers the drive voltage of the device and increases the charge injection efficiency. Polyethylene dioxythiophene (PEDOT: PSS) doped with polystyrene sulfonic acid (PSS) is widely used for polymers, and phthalocyanine-based copper phthalocyanine (CuPc) is widely used for low molecules.

<Hole transport layer>
The hole transport layer serves to transport holes injected from the hole injection layer to the light emitting layer. It is necessary to have an appropriate ionization potential and hole mobility. Specifically, the hole transport layer may be a triphenylamine derivative, N, N′-bis (1-naphthyl) -N, N′-diphenyl-1,1′-biphenyl-4,4′-diamine (NPD ), N, N′-diphenyl-N, N′-bis [N-phenyl-N- (2-naphthyl) -4′-aminobiphenyl-4-yl] -1,1′-biphenyl-4,4 ′ -Diamine (NPTE), 1,1-bis [(di-4-tolylamino) phenyl] cyclohexane (HTM2) and N, N'-diphenyl-N, N'-bis (3-methylphenyl) -1,1 '-Diphenyl-4,4'-diamine (TPD) or the like is used. The thickness of the hole transport layer is preferably 10 nm to 150 nm. The thinner the thickness is, the lower the voltage can be. However, the thickness is particularly preferably 10 nm to 150 nm from the problem of short circuit between electrodes.

<Light emitting layer>
The light-emitting layer uses a material that provides a field where injected electrons and holes are recombined and has high emission efficiency. More specifically, the light-emitting host material and the light-emitting dye doping material used in the light-emitting layer function as recombination centers of holes and electrons injected from the anode and the cathode, and light emission to the host material in the light-emitting layer The doping of the dye obtains high luminous efficiency and converts the emission wavelength. These are required to have an appropriate energy level for charge injection, excellent in chemical stability and heat resistance, and to form an amorphous thin film homogeneously. In addition, it is required that the type and color purity of the luminescent color are excellent and the luminous efficiency is high. Light emitting materials that are organic materials include low-molecular materials and high-molecular materials. In the case of a low molecular material, it is formed by vapor deposition, and in the case of a high molecular material, it is formed by a coating method. Further, it is classified into a fluorescent material and a phosphorescent material according to the light emission mechanism. Specifically, the light-emitting layer comprises tris (8-quinolinolato) aluminum complex (Alq ₃ ), bis (8-hydroxy) quinaldine aluminum phenoxide (Alq ′ ₂ OPh), bis (8-hydroxy) quinaldine aluminum— 2,5-dimethylphenoxide (BAlq), mono (2,2,6,6-tetramethyl-3,5-heptanedionate) lithium complex (Liq), mono (8-quinolinolato) sodium complex (Naq), Mono (2,2,6,6-tetramethyl-3,5-heptanedionate) lithium complex, mono (2,2,6,6-tetramethyl-3,5-heptanedionate) sodium complex and bis ( 8-quinolinolato) calcium complex (CAQ ₂₎ metal complexes of quinoline derivatives such as tetraphenyl butadiene, E D Lucina click polyhedrin (QD), anthracene, and a fluorescent substance such as perylene and coronene. As the host material, a quinolinolate complex is preferable, and an aluminum complex having 8-quinolinol and its derivative as a ligand is particularly preferable.

<Electron transport layer>
The electron transport layer serves to transport electrons injected from the electrode. Specifically, the electron transport layer is formed of a quinolinol aluminum complex (Alq ₃ ), an oxadiazole derivative (for example, 2,5-bis (1-naphthyl) -1,3,4-oxadiazole (BND) and 2 -(4-t-butylphenyl) -5- (4-biphenyl) -1,3,4-oxadiazole (PBD) and the like), triazole derivatives, bathophenanthroline derivatives, silole derivatives and the like are used.

<Electron injection layer>
The electron injection layer is required to increase the electron injection efficiency. Specifically, the electron injection layer is provided with a layer doped with an alkali metal such as lithium (Li) or cesium (Cs) at the cathode interface.

<Reflective electrode (second electrode)>
A metal having a small work function or an alloy thereof is used for the second electrode which is a reflective electrode (cathode). Specific examples of the second electrode include alkali metals, alkaline earth metals, and metals belonging to Group 3 of the periodic table. Of these, aluminum (Al), magnesium (Mg), or alloys thereof are preferably used because they are inexpensive and have good chemical stability. In addition, a co-deposited film of Al, MgAg, a laminated electrode obtained by depositing Al on a thin film deposited film of LiF or Li ₂ O, or the like is used. In the polymer system, a laminate of calcium (Ca) or barium (Ba) and aluminum (Al) is used.
Needless to say, the reflective electrode as the second electrode may be used as the anode.
In the fired product, the bubbles in the glass layer are spherical and the surface is also smooth.

(Example)
Hereinafter, the present invention will be described more specifically according to examples of the present invention. In addition, this invention is not limited to a following example.

[Method of forming a thin film mainly composed of tin oxide]
As described below, the method for forming a thin film containing tin oxide as a main component is a method of forming a tin oxide thin film on a glass ribbon by online forming, and a tin oxide thin film on the glass substrate after the glass substrate is formed. There is a method of molding.
First, a method for forming a tin oxide thin film having irregularities on the surface thereof on a glass ribbon will be described. First, using a bath and using a sheet glass manufacturing apparatus by a usual float method, a tin oxide thin film having irregularities on the surface mainly composed of tin oxide is formed on a glass ribbon by online molding. A buffer layer is formed. First, ordinary glass raw materials such as silica sand are heated and melted in a melting furnace, and the molten glass is introduced into a bath filled with molten tin. Since glass has a lower specific gravity than tin, the glass ribbon floats on the molten tin in the bath. The inside of the bath is filled with a mixed gas of 98% by volume of nitrogen gas and 2% by volume of hydrogen gas, and is maintained at a pressure slightly higher than atmospheric pressure.
Thus, the glass ribbon is pulled in the direction of the slow cooling line, and the first electrode 102 and the buffer layer 103 made of a transparent conductive film are formed by a coater in the middle (see FIG. 2). The mechanical structure of the coater is all formed similarly. Here, a mixed gas of a raw material gas and a carrier gas is blown toward the glass ribbon from the supply nozzle, and this mixed gas flows toward the exhaust port while traveling on the glass ribbon. At this time, the glass ribbon is in a considerably high temperature state, and a thin film (transparent conductive film) is formed (crystal growth) using the heat.
Next, a method for forming a tin oxide thin film having irregularities on its surface on a glass substrate will be described. A glass substrate of a predetermined size is prepared and thoroughly cleaned. Next, the glass substrate is heated to a high temperature, and a hydrolysis reaction between tin tetrachloride and water is performed on the glass substrate surface by atmospheric pressure CVD to form a tin oxide transparent conductive film (fluorine-doped tin oxide film). At this time, the glass substrate is in a high temperature state, and a thin film (transparent conductive film) is formed (crystal growth) using the heat.
Thus, a translucent substrate provided with a translucent electrode (first electrode) is obtained using any of the above methods.
Then, a layer (organic layer 110) having a light emitting function such as a hole injection layer, a light emitting layer, and an electron injection layer is formed by, for example, a vapor deposition method.

In this manner, a layer having a light emitting function composed of the organic layer 110 is formed on the light-transmitting first electrode 102, and a reflective second electrode 120 is formed on the upper layer to form a light-emitting region. Then, a bottom emission type organic LED light emitting element is formed which extracts light to the glass substrate 101 side. This light-emitting region is formed by overlapping a light-transmitting layer composed of a light-transmitting first electrode 102 and an organic layer 110 formed thereon, and a reflective second electrode 120 formed thereon. Area.

In the case of the organic LED light emitting device of the present embodiment, a layer having a light emitting function, that is, a hole injection layer, a light emitting layer, and an electron injection layer is usually sandwiched between the first electrode and the second electrode. Here, this constitutes a functional element. Needless to say, the layer having a light emitting function is not limited to a dry process such as an evaporation method, but can be applied to a layer formed by a wet process such as a coating method. Of course, the present invention is not limited to this five-layer structure, and is not limited to an organic LED light-emitting element, as long as it is a functional element having an electrode on at least the substrate side.

Known materials and structures are used for the hole injection layer, the light emitting layer, the electron injection layer, and the like. The first electrode is a translucent electrode, but the second electrode may be a translucent electrode or a reflective electrode.
The translucent electrode can be used with tin oxide or other materials in addition to the above-mentioned ITO. Various metallic electrodes can be used as the reflective electrode as the second electrode 120, but typical materials include aluminum, an AgMg alloy, and Ca.

Prepare a soda-lime glass substrate (30 cm x 40 cm x 1.1 mm) with a silica film with a thickness of about 50 nm as an alkali barrier layer (a layer that prevents the diffusion of alkali components from the substrate), and wash it thoroughly. Thereafter, a hydrolysis reaction between tin tetrachloride and water was performed by an atmospheric pressure CVD method to form a tin oxide transparent conductive film (fluorine-doped tin oxide film). Specifically, the following procedure was used. Tin tetrachloride was placed in a bubbler tank maintained at 55 ° C., and nitrogen was introduced from a cylinder to vaporize it. Water was supplied from a boiler maintained at 10 ° C. or higher. Both were heated to 150 ° C. and then transported to the injector body via a conduit kept at 150 ° C. and mixed. The mixing ratio (mol ratio) was tin tetrachloride / water = 1/10. The temperature of the injector body was kept at about 150 ° C. by a heat medium (oil). The mixed gas was discharged from the injector discharge portion onto a glass substrate at about 500 ° C., and a tin oxide transparent conductive film was formed on the glass substrate surface.

On this upper layer, a buffer layer 103 made of P-DOT / PSS (mixture of polythiophene and polystyrene sulfonic acid) is formed by a coating method. And this was cut | disconnected to a suitable magnitude | size and it was set as the sample. This sample was placed on an imaging stand with an inclination of 30 °, and the surface shape was photographed using an SEM from the vertical direction. The photograph is shown in FIG.

The number, spacing, and height of protrusions (polygonal pyramids and plateau-shaped protrusions) having a height of 100 nm or more were measured on the SEM photograph having a magnification of 20,000. The height was measured by taking a cross section and using an AFM photograph, but the cross section may be cut out and an SEM photograph taken. As a result, the average number of protrusions on the surface of the thin film was about 20 per 1 μm □. Here, since the width W1 is about 200 nm, H1 / W1 is about 0.5.

Thus, as shown in FIG. 2, a translucent substrate having a first electrode (translucent electrode) having a surface shape having regular pyramid-shaped projections can be obtained, and light extraction is performed. The efficiency is 50% or more, and a substrate for an organic LED light emitting element with high light extraction efficiency is formed.
Further, according to the present invention, in the organic LED light emitting element, the convexity of the first electrode increases the refraction by increasing the area of the inclined portion of the angled portion by forming a conical shape with a sharp tip. Can do.

According to the present invention, the light-transmitting electrode (first electrode) is formed with a pyramid-shaped convex and has a light scattering effect, so that the above-described light can be obtained over the entire emission spectrum range (430 nm to 650 nm). The extraction efficiency can be improved. This is because the probability that light propagating inside the device changes its direction by scattering and is emitted to the outside increases. Further, even when propagating through the element at an angle that cannot be extracted to the outside, the light is reflected by the reflective electrode and the light reaches the translucent electrode again.

In order to further improve the light extraction efficiency, it is desirable that the refractive index of the glass substrate be equal to or higher than the refractive index of the first electrode material. This is because when the refractive index is low, a loss due to total reflection occurs at the interface between the glass substrate and the first electrode material. The refractive index of the glass substrate only needs to exceed at least a part of the emission spectrum range of the light emitting layer (eg, red, blue, green, etc.), but exceeds the entire emission spectrum range (430 nm to 650 nm). It is more desirable that it exceeds the entire visible light wavelength range (360 nm to 830 nm).
The P-DOT / PSS used here is effective as a buffer layer, but also has a role as a charge injection layer.

Further, as shown in the enlarged view of the main part of the projection T1 in FIG. 4, the ratio of the average value H1 of the height to the average value W1 of the appearance interval of the projection T1 on the surface of the first electrode is 0.5 or more. Is desirable.
Here, when the ratio of the average value H1 of the height to the average value W1 is less than 0.5, the unevenness on the surface of the buffer layer formed in the upper layer is hardly formed to a desired value. By setting this level, film formation can be facilitated in a state where the unevenness on the electrode surface is larger than the unevenness on the surface of the buffer layer. With this configuration, the light extraction efficiency can be improved more favorably.
Furthermore, the surface roughness Ra of the surface on the buffer layer side of the first electrode is preferably 60 nm or more.

The surface roughness Ra of the buffer layer side surface of the first electrode is more desirably 80 nm or more and less than 120 nm. If the surface roughness is larger than 120 nm, a short circuit may occur.
Since the thickness of the light emitting layer is 100 to 150 nm, the surface roughness of the buffer layer is desirably 80 nm or more and less than 120 nm rather than the light emitting layer. If the surface roughness of the buffer layer is greater than 120 nm, a short circuit may occur.
Further, the appearance interval of the protrusion T2 on the buffer layer side surface formed on the first electrode is 0.1 to 0.3 μm.
According to this configuration, light extraction with good visibility can be performed without incurring wavelength dependency.

Thereafter, an organic layer 110 is sequentially formed by a coating method as a layer having a light emitting function by a usual method, and a second electrode 120 made of a reflective electrode is further formed. As shown in FIG. Is formed.

Further, as shown in FIG. 1, the buffer layer 103 has a smaller surface roughness at the interface with the organic layer 110 as a layer having a light emitting function than the interface with the surface of the light-transmitting first electrode 102. Things are desirable. Further, it is desirable that the surface of the buffer layer 103 forms an uneven surface, and the ratio of the average value H2 of the height to the average value W2 of the appearance interval of the convex T2 is 0.2 or more.
In addition, the organic layer 110 that is a layer having a light emitting function has an uneven surface on the second electrode 120 side surface, and the ratio of the average value of the height H3 to the average value of the appearance intervals W3 of the protrusions T3 is 0.1. The above is desirable.

In the organic LED light-emitting device formed as described above, the output peak wavelength λ of the layer having the light emitting function satisfies the following formula.
(Λ <450 nm) (formula)

Therefore, according to the glass substrate provided with the thin film of tin oxide doped with fluorine of Example 1, when used as an organic LED element, the light confinement effect of visible light is effectively exhibited.

Note that the P-DOT / PSS used here is effective as the buffer layer 103. However, by using an oxide of a refractory metal such as molybdenum oxide as the buffer layer 103, the buffer layer has a charge injection effect. Therefore, higher efficiency can be achieved.
In addition, the organic layer 110 as a layer having a light emitting function can be formed by a coating method or a dry process such as an evaporation method.
In addition, since molybdenum oxide has a small specific resistance and a specific resistance close to that of the first electrode, a voltage drop in the buffer layer can be ignored, and an electric field is generated between the buffer layer 103 and the second electrode 120. Get bigger in between. Further, the pointed cone-shaped tip of the first electrode surface is relaxed by the buffer layer. Therefore, the presence of the buffer layer 103 further reduces the electric field concentration and improves the lifetime. On the other hand, the refractive index differs greatly at the interface between the first electrode 102 and the buffer layer 103 on the substrate 101, and the scattering effect is improved at this portion. Further, since there is a difference in refractive index at the interface between the buffer layer and the layer having a light emitting function (organic layer 110) and there are irregularities, the scattering effect is high. For this reason, two-stage scattering occurs on the first electrode side, and the light extraction efficiency is improved.

As described above, according to the organic LED light emitting element of the present embodiment, it is possible to form a film so as to maintain unevenness even at the interface between the second electrode on the upper layer side and the layer having a light emitting function. As described above, the unevenness is formed at the interface between the organic layer and the second electrode, so that the diffusibility at the interface between the organic layer and the second electrode can be increased, and further light extraction is performed. Efficiency can be improved. For example, when the second electrode is a translucent electrode and light is extracted from both sides, light extraction in both directions is good.
In addition, the film can be formed so as to maintain unevenness at the interface between the second electrode on the upper layer side and the layer having a light emitting function, and unevenness is formed at the interface between the organic layer and the second electrode. Therefore, when the second electrode on the upper layer side is a reflective electrode, the reflection direction at the interface between the organic layer and the second electrode becomes multi-directional, and the first electrode is moved from the organic layer. As a result, it is possible to increase the light traveling toward the substrate side, and to further improve the light extraction efficiency.

(Embodiment 2)
Next, a second embodiment of the present invention will be described.
FIG. 7 is a cross-sectional view showing a substrate for an organic LED light-emitting element according to Embodiment 2 of the present invention, and FIG. 8 is a cross-sectional view showing the organic LED light-emitting element according to Embodiment 2 of the present invention.
In the first embodiment, the unevenness on the surface is formed so that the edge is sharp even on the buffer layer. However, as shown in FIG. 7, the buffer layer is more uneven than the unevenness on the surface of the translucent first electrode 102. The unevenness on 103P may be a gentler shape.
According to this configuration, even when the layer having the light emitting function formed on the upper layer is thin, no disconnection occurs.
Further, the unevenness on the buffer layer 103P may be smaller than the unevenness on the surface of the light-transmitting first electrode 102, but the unevenness shape may be gentle to the same extent.

As described above, in the present embodiment, as shown in FIG. 8, the unevenness of the surface of the light-transmitting first electrode 102 is applied with the buffer layer 103P formed of P-DOT / PSS, so that the surface is slightly gentle. Then, the organic layer 110, which is a layer having a light emitting function, is formed on the upper layer so that the unevenness of the surface becomes slightly gentle. That is, the buffer layer 103P is characterized in that the surface roughness at the interface with the organic layer 110 which is a layer having a light emitting function is slightly smaller than the interface with the surface of the translucent electrode which is the first electrode 102. To do.

Also in this embodiment, the unevenness is formed at the interface between the organic layer 110 and the second electrode 120, so that the reflection direction at the interface between the organic layer 110 and the second electrode 120 is multidirectional. Thus, further increase in light traveling from the organic layer 110 to the substrate side through the first electrode 102 can be achieved.
That is, the unevenness on the surface of the organic layer 110 is smaller than the unevenness on the surface of the first electrode 102, but the distance between the electrodes gently changes at the same pitch, so that a large voltage is applied locally. It can be avoided.
As described above, by forming irregularities on the surface of the first electrode 102, the interface between the first electrode and the buffer layer 103P, the interface between the buffer layer 103P and the organic layer 110, the organic layer 110 and the second electrode While long-term reflection is repeated at each of the interfaces with 120, a long life can be maintained and light can be extracted efficiently.

According to this configuration, even when the layer having a light emitting function formed on the buffer layer 103P is thin, no disconnection occurs.

Further, as the surface of the buffer layer and the surface of the layer having a light emitting function are moved from the surface of the first electrode to the surface of the layer having the light emitting function, the unevenness gradually decreases, and the surface of the layer having the light emitting function becomes the surface of the first electrode. By maintaining the unevenness corresponding to the unevenness, it is possible to provide an organic LED light-emitting element with good light extraction efficiency and higher reliability.

Further, since the unevenness is formed not on the surface of the substrate 101 but on the surface of the first electrode 110, scattering occurs at a position closer to the light emitting region, and the light extraction characteristics are further improved.
In FIG. 8, a region indicated by a solid line arrow is a region where an electric field is substantially applied, and a region indicated by a broken line arrow is a distance between electrodes. This is because, since the specific resistance of the buffer layer 103P is small, the electric field applied to the buffer layer 103P is extremely small, and the electric field applied to the organic layer 110 occupies most of the electric field. The distance between the solid-line arrows is the distance between the electrodes where the electric field is applied substantially, and the broken-line arrow is the optical interface having a scattering effect, and the surface of the translucent electrode (first electrode) and the reflective electrode (first Corresponds to the distance from the surface. From this figure, it can be seen that the electrical interface has a uniform spacing, while the optical interface has irregularities. Accordingly, the scattering effect can be enhanced while maintaining the lifetime.

(Embodiment 3)
Next, a third embodiment of the present invention will be described.
FIG. 9 is a cross-sectional view showing a substrate for an organic LED light-emitting element according to Embodiment 3 of the present invention, and FIG. 10 is a cross-sectional view showing the organic LED light-emitting element according to Embodiment 3 of the present invention.
In the second embodiment, the unevenness on the buffer layer 103P has a gentler shape than the unevenness on the surface of the translucent first electrode 102. However, the organic LED light emission of this embodiment As shown in FIGS. 9 and 10, the element is characterized in that a low-resistance buffer layer 103Q is used and the surface of the buffer layer 103Q is substantially flat.
According to this configuration, the layer having the light emitting function formed on the upper layer is formed on the flat surface, and even when the layer having the light emitting function is thin, the lower layer is covered with the layer having the light emitting function. Does not become insufficient.

As described above, in the present embodiment, as shown in FIG. 9, the unevenness of the surface of the light-transmitting first electrode 102 is provided with the buffer layer 103Q configured by the highly doped low resistance P-DOT / PSS. By applying and forming, the surface is flattened, and the organic layer 110 which is a layer having a light emitting function is formed thereon. That is, the buffer layer 103Q has a flat surface without depending on the surface roughness at the interface with the organic layer 110 which is a layer having a light emitting function, rather than the interface with the surface of the transparent electrode which is the first electrode 102. It is characterized by having it.

In this embodiment, the unevenness on the surface of the organic layer 110 is smaller than the unevenness on the surface of the first electrode 102, but the distance between the electrodes gently changes at the same pitch, and the buffer layer is an insulating layer. Therefore, the substantial thickness of the organic layer 110 is constant, and it is possible to avoid a situation in which a large voltage is applied locally.
As described above, by forming irregularities on the surface of the first electrode 102, multi-directional reflection is repeated at the interface between the first electrode and the buffer layer 103Q and the interface between the buffer layer 103Q and the organic layer 110, respectively. However, a long life can be maintained and light can be extracted efficiently.

Further, the unevenness of the surface of the first electrode is substantially flat on the surface of the buffer layer, and the buffer layer is made of a low resistance material, so that the substantial distance between the electrodes is the surface of the flat buffer layer. To the distance between the second electrodes.
In this way, it is possible to provide a more reliable organic LED light-emitting element with good light extraction efficiency and no power concentration.

Note that a low-resistance inorganic material such as molybdenum oxide has a small specific resistance and a specific resistance close to that of the first electrode, so that a voltage drop in the buffer layer can be ignored. Between the two electrodes 120. Further, the pointed cone-shaped tip of the first electrode surface is relaxed by the buffer layer. Accordingly, due to the presence of the buffer layer 103, the distance between the buffer layer 103 and the second electrode 120 becomes substantially uniform, the electric field concentration is further reduced, and the lifetime is improved. On the other hand, the refractive index differs greatly at the interface between the first electrode 102 and the buffer layer 103 on the substrate 101, and the scattering effect is improved at this portion. Further, since there is a difference in refractive index at the interface between the buffer layer and the layer having a light emitting function (organic layer 110) and there are irregularities, the scattering effect is high. For this reason, two-stage scattering occurs on the first electrode side, and the light extraction efficiency is improved. For example, by using molybdenum oxide having a specific resistance of 8.1 × 10 ⁻⁵ Ω, which is formed by, for example, MoCVD, as a buffer layer and using ITO of 1.5 × 10 ⁻⁴ Ω as the first electrode, An organic LED light-emitting element that can achieve the effect can be obtained.

In addition, according to the present invention, by selecting a material having a specific resistance close to that of the translucent electrode and having a large refractive index difference from the translucent electrode, an (electrical) interface when an electric field is applied And the optical interface serving as the scattering surface can be shifted. FIG. 10 shows a region where an electric field is actually applied by a solid arrow, and a distance between electrodes by a broken arrow. The distance between solid line arrows corresponds to the distance between electrodes to which an electric field is applied, and the broken line arrow corresponds to the distance between optical interfaces. Therefore, the electrical interface is flattened while leaving the unevenness in the optical interface, so that the distance between the electrodes of the organic LED light emitting element is maintained substantially uniform, and in the vicinity of the layer having the light emitting function. The scattering effect can be enhanced, and the light extraction efficiency can be improved and the life can be extended.

In the above-described embodiment, the organic LED light emitting element having a bottom emission structure that extracts light to the substrate side has been described. However, the present invention is not limited to this, and light generated by unevenness at the interface between the first electrode and the layer having a light emitting function. Double-sided organic LED light emission that not only improves the extraction characteristics, but also uses the second electrode as a translucent electrode to improve the light extraction characteristics due to irregularities at the interface between the second electrode and the layer having a light emitting function. It can also be applied to elements.
Although an organic layer is used as a layer having a light emitting function, an inorganic film such as an inorganic film made of a refractory metal oxide such as molybdenum oxide may be used as a buffer layer.

Although the present invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.

This application is based on a Japanese patent application (Japanese Patent Application No. 2010-0500162) filed on Mar. 8, 2010, the contents of which are incorporated herein by reference.

As described above, the organic LED light emitting element of the present invention can increase the light extraction efficiency and can be applied to various light emitting devices such as a display panel.

100 Translucent substrate with electrode 101 Substrate 102 First electrode (translucent electrode)
103, 103P, 103Q Buffer layer 110 Organic layer (layer having light emitting function)
120 Second electrode (reflective electrode)

Claims

A translucent substrate;
A first electrode formed on the light-transmitting substrate by a CVD method and made of a light-transmitting oxide film having irregularities on the surface;
A buffer layer formed on the first electrode;
A layer having a light emitting function formed on the buffer layer;
An organic LED light emitting device comprising: a second electrode formed on the layer having a light emitting function.
The organic LED light-emitting device according to claim 1,
The surface of the buffer layer is an organic LED light emitting element having irregularities corresponding to the irregularities of the surface of the first electrode.
The organic LED light-emitting device according to claim 2,
The surface of the layer having a light emitting function has unevenness corresponding to the unevenness of the surface of the first electrode,
The unevenness on the surface of the first electrode, the unevenness on the surface of the buffer layer, and the unevenness on the surface of the layer having the light emitting function are:
An organic LED light-emitting element in which the surface roughness representing the degree of each unevenness decreases sequentially from the surface of the first electrode to the surface of the buffer layer and the surface of the layer having a light emitting function.
It is an organic LED light emitting element of any one of Claims 1 thru | or 3, Comprising:
Of the irregularities on the surface of the first electrode, the convexes are organic LED light emitting elements having a regular pyramid shape.
The organic LED light-emitting device according to claim 4,
The organic LED light emitting element whose ratio of the average value H1 of the said convex height with respect to the average value W1 of the convex appearance interval of the said 1st electrode surface is 0.5 or more.
It is an organic LED light emitting element of any one of Claims 1 thru | or 5, Comprising:
The organic LED light emitting element whose surface roughness Ra of the said 1st electrode surface is 60 nm or more.
The organic LED light-emitting device according to claim 6,
The organic LED light emitting element whose surface roughness Ra of the said 1st electrode surface is 80 nm or more and less than 120 nm.
The organic LED light-emitting device according to claim 6,
An organic LED light-emitting element in which a convex appearance interval on the surface of the first electrode is 0.1 to 0.3 μm.
It is an organic LED light emitting element of any one of Claims 1 thru | or 8, Comprising:
The organic LED light emitting element whose said buffer layer is a solution application type organic layer.
It is an organic LED light emitting element of any one of Claims 1 thru | or 8, Comprising:
The organic LED light emitting element whose said buffer layer is a metal oxide thin film.
The organic LED light-emitting device according to claim 4,
The organic LED light emitting element whose ratio of the average value H2 of the said convex height with respect to the average value W2 of the convex appearance interval among the unevenness | corrugations of the said buffer layer surface is 0.2 or more.
The organic LED light-emitting device according to claim 11,
The organic LED light emitting element whose ratio of the average value H3 of the said convex height with respect to the average value W3 of the convex appearance interval among the unevenness | corrugations of the layer surface which has the said light emission function is 0.1 or more.
It is an organic LED light emitting element of any one of Claims 1 thru | or 12, Comprising:
The organic LED light emitting element whose said translucent board | substrate is a glass substrate.
It is an organic LED light emitting element of any one of Claims 1 thru | or 12, Comprising:
The organic LED light emitting element whose said translucent board | substrate is a flexible substrate.
The organic LED light-emitting element according to claim 1,
The first electrode is an organic LED light-emitting element composed of a fluorine-doped tin oxide layer.
Forming a first electrode made of a light-transmitting oxide film having irregularities on the surface, formed by a CVD method on a light-transmitting substrate;
Forming a buffer layer on the first electrode;
Forming a layer having a light emitting function on the buffer layer;
And a step of forming a second electrode on the layer having the light emitting function.
A method for producing an organic LED light-emitting device according to claim 16,
The step of forming the buffer layer is a concavo-convex corresponding to the concavo-convex of the surface of the first electrode, forming a smaller concavo-convex on the surface of the buffer layer,
The step of forming the layer having a light emitting function is unevenness corresponding to the unevenness on the surface of the buffer layer, and is smaller than the unevenness on the surface of the buffer layer. The manufacturing method of the organic LED light emitting element which is the process of forming into a film so that an unevenness | corrugation may be formed in the layer surface which has the said light emission function.