JP2014082024A - Organic light emitting element and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: an organic light emitting element high in life and reliability, by solving such problems as mass productivity and easiness in manufacturing, by improving light extraction efficiency of a surface light emitting element in which an OLED is used, and by improving yield; and a method for manufacturing the organic light emitting element.SOLUTION: An organic light emitting element includes a first transparent electrode, an organic thin film layer and a second transparent electrode which are sequentially laminated on a light emitting element substrate, and a reflective mirror layer on the outermost surface on a side opposite to a light extraction surface. The light emitting element substrate is provided with a transparent support substrate and a high refractive index layer arranged between the support substrate and the transparent electrode and having one or two or more layers having a refractive index higher than that of the support substrate, and the high refractive index layer scatters light incident from the transparent electrode side.

Description

  The present invention relates to an organic light emitting device and a method for manufacturing the same.

  In recent years, flat panel displays have been actively developed. As a typical example of a surface light emitting element that is a light emitting element used in such a flat panel display, an organic electroluminescence element (OLED) can be given. An OLED is a light-emitting element that uses electroluminescence of a solid fluorescent substance, but has a laminated structure of materials having different refractive indexes, and therefore, due to the influence of reflection at the interface, the radiation efficiency of light to the outside ( There is a problem that the light extraction efficiency is low.

  When the light extraction efficiency is calculated by simple calculation, the ratio of the light that is confined in each layer and cannot be extracted to the outside and the ratio of the light that is radiated to the outside is approximately as guided light that is confined in the transparent electrode or organic thin film layer and cannot be extracted. 45%, which is about 35% of the waveguide light that is confined in the substrate and cannot be extracted, it can be seen that only about 20% of the emitted light can be extracted to the outside. Similar results are described in Non-Patent Document 1, for example.

  Thus, many examples have been proposed to solve the above-described problems by providing means for converting the light emission angle on the substrate of the OLED. Specifically, a diffraction grating structure is produced on a substrate to prevent reflection with respect to light of a specific wavelength, and a similar effect can be obtained by introducing a lens structure on the substrate surface to improve the extraction efficiency. What you expect. Although these techniques have a certain effect in improving the extraction efficiency, it is necessary to actively create a complicated fine structure, and thus it is difficult to apply them practically in the manufacturing process.

  On the other hand, for example, Patent Document 1 proposes to use a special glass base material having a refractive index comparable to that of the transparent conductive film to eliminate the thin-film guided light and improve the extraction efficiency. . When a structure such as a lens is provided on the light emission side opposite to the organic thin film layer of the substrate, the thin film guided light remains in the layer and cannot be extracted. There is an advantage in that it is possible to take out the thin-film guided light. However, in order to industrially mass-produce special high refractive index substrates as used in Patent Document 1, it is very expensive and difficult to put into practical use.

  As another method for reducing the thin-film guided light, a structure in which the refraction angle can be changed between the substrate and the transparent conductive film (ITO (Indium Tin Oxide), etc.) by a diffraction grating or a scattering structure is used. A method of forming and inserting is conceivable. In such a case, it is difficult to directly form a transparent electrode film so as to follow the structure on the substrate, so the surface of the base material is flattened using a material having a refractive index equivalent to that of the transparent electrode. Need to do.

  For example, Patent Document 2 proposes that an inorganic EL element is manufactured by using a spin-on-glass (SOG) material on a substrate having random unevenness as a substrate for an inorganic EL element, using a Spin On Glass (SOG) material. In Patent Document 3, a substrate having a surface roughness Ra = 0.01 to 0.6 μm is formed by depositing SiN having a high refractive index of 0.4 to 2 μm using a chemical vapor deposition (CVD) method. It has been proposed to produce an organic EL element as a substrate material, reduce thin-film guided light, and improve light extraction efficiency.

  Furthermore, as another method for reducing thin film guided light, for example, Patent Document 4 proposes forming a high refractive index glass layer containing a scattering component such as air between ITO and a substrate. ing.

  However, the inventions disclosed in Patent Documents 2 to 4 are techniques for improving waveguide loss and are not related to measures against plasmon loss.

  In contrast to the inventions disclosed in Patent Documents 2 to 4, Patent Document 5 discloses that the thickness of the organic layer is greater than 250 nm, preferably greater than 400 to 500 nm. We are trying to reduce plasmon loss by separating the layers.

Further, in Patent Documents 6 to 8, an attempt is made to reduce plasmon loss by a structure in which an element sandwiched between transparent electrodes and a reflecting mirror are combined so that the reflected light is not totally reflected directly.

JP 2009-238507 A Japanese Patent Laid-Open No. 10-241856 JP 2003-297572 A International Publication No. 2009/017035 JP 2008-543074 A JP 2011-233288 A JP 2011-233289 A JP 2011-243625 A JP 2003-249353 A

Advanced Material 6 page 491 (1994)

  However, the method of extending the distance to the reflective electrode disclosed in Patent Document 5 with an organic film is realized because the organic light emitting layer and the element itself are thickened, and the applied voltage required for light emission increases. Not right. In the invention disclosed in Patent Document 5, an organic material that functions as an element is used to increase the distance to the reflective electrode. However, in this method, the carrier mobility of the organic material is high and the resistance value is not low. The element efficiency decreases due to voltage increase or the like.

  Further, Patent Documents 6 to 8 do not disclose any special measures when forming a transparent electrode on an organic material. For example, it is not realistic to form a metal oxide film such as ITO with high transmittance or a polymer conductive film such as PEDOT because the organic thin film layer is damaged. In Patent Documents 6 and 7, it is unclear how to form a transparent electrode on the organic layer. For example, in a general method such as sputtering, the organic layer is damaged, so that the device characteristics are remarkably deteriorated.

  Furthermore, in the method described in Patent Document 9, a polymer material PEDOT: PSS or PANI is spin-coated as a protective layer for reducing damage by the direct current sputtering method, but in this method, as described above, Since it damages the organic thin film layer, it is not realistic. Further, the dispersion of fine particles in a transparent electrode or an organic material has a problem that the yield is remarkably deteriorated in producing an element.

  Accordingly, the present invention has been made in view of the above-described present situation, and solves the above-described problems such as mass productivity and ease of manufacture, and improves the light extraction efficiency of a surface light emitting device using an OLED. An object of the present invention is to provide an organic light emitting device with improved yield and high lifetime and reliability and a method for manufacturing the same.

  As a result of intensive studies to solve the above problems, the present inventor formed a glass layer having a light scattering function for increasing the extraction efficiency on the surface of a support substrate such as a glass substrate, and on this glass layer. A light emitting element substrate is formed using a glass paste composition containing a low melting point glass frit having a refractive index equal to or higher than the refractive index of the support substrate as a planarizing material for planarizing the interface with the first transparent electrode to be formed, The second transparent electrode is formed through the organic light emitting layer so as to form a counter electrode with the first transparent electrode, and the reflection mirror layer is formed on the outermost surface opposite to the light extraction surface, thereby greatly reducing the plasmon loss. It has been found that it can be reduced or suppressed and light extraction loss can be reduced.

  In addition, the present inventor can reduce damage to the organic light emitting layer by using a film forming method capable of sublimating a high melting point material such as an ion beam sputtering method or an electron beam plasma deposition method for the transparent electrode. And succeeded in forming the second transparent electrode directly on the organic light emitting layer.

  In addition, as a result of further studies, the inventor of the present invention uses an organic film forming method capable of forming a sublimation film by forming a protective layer between the organic light emitting layer and the second transparent electrode. It has been found that damage to the light emitting layer can be completely suppressed, and the present invention has been completed based on these findings.

  That is, according to an aspect of the present invention, the first transparent electrode, the organic thin film layer, and the second transparent electrode are sequentially stacked on the light emitting element substrate, and the reflection mirror layer is formed on the outermost surface opposite to the light extraction surface. The light-emitting element substrate is disposed between a transparent support substrate and the support substrate and the transparent electrode, and has a refractive index equal to or higher than the refractive index of the support substrate. And an organic light emitting device characterized in that the high refractive index layer scatters light incident from the transparent electrode side.

  According to another aspect of the present invention, the first transparent electrode, the organic thin film layer, and the second transparent electrode are sequentially stacked on the light emitting element substrate, and the reflection mirror is disposed on the outermost surface opposite to the light extraction surface. An organic light emitting device having a layer, wherein the light emitting device substrate is disposed between a transparent support substrate and the support substrate and the transparent electrode, and has a refractive index equal to or higher than a refractive index of the support substrate. A refractive index layer, and the high refractive index layer has a light scattering portion for scattering light incident from the transparent electrode side, and a flat surface in contact with the transparent electrode, and the high refractive index layer The diameter of the bubble present is 1/10 or less of the thickness of the layer adjacent to the transparent electrode among the layers constituting the high refractive index layer, and the proportion of the bubbles in the layer adjacent to the transparent electrode is The bubbles for the entire area of the horizontal cross section of the layer adjacent to the transparent electrode The ratio of the area of the horizontal cross section is 0.5% or less, and the ratio of the area of the vertical cross section of the bubbles to the total area of the vertical cross section of the layer adjacent to the transparent electrode is 0.5% or less. Is provided.

  In each of the light emitting element substrates, the interface between the support substrate and the high refractive index layer may be an uneven surface.

  In this case, it is preferable that the film thickness of the high refractive index layer is 30 times or more the average surface roughness Ra of the uneven surface.

  Moreover, it is preferable that the film thickness of the said high refractive index layer is 1.3 times or more of the maximum surface roughness Rz of the said uneven surface.

  The film thickness of the high refractive index layer is preferably 3 μm or more and 100 μm or less.

  Moreover, it is preferable that average surface roughness Ra of the said uneven | corrugated surface is 0.7 micrometer or more and 5 micrometers or less.

  Further, the uneven shape of the uneven surface may be a pyramid shape or a lens shape.

  The high refractive index layer may consist of only one layer.

  Alternatively, the high refractive index layer is adjacent to the support substrate and includes at least a light scattering layer having the light scattering portion, and a planarization layer adjacent to the transparent electrode and having the flat surface. It may consist of layers. At this time, the light scattering layer may contain a glass material and a scattering material having a refractive index different from that of the glass material.

  In addition, the light scattering layer that does not have an uneven surface at the interface between the support substrate and the high refractive index layer, the high refractive index layer is adjacent to the support substrate and has the light scattering portion, and the transparent electrode. The light scattering layer contains a glass material and a scattering material having a refractive index different from that of the glass material. May be.

  The first transparent electrode and the second transparent electrode may be made of ITO (Indium Tin Oxide), tin oxide, zinc oxide, IZO (Indium Zinc Oxide), AZO (Aluminum-doped Zinc Oxide), or GZO (Gallium), respectively. -Doped Zinc Oxide) is preferable.

  The thickness of the second transparent electrode differs depending on the physical properties such as refractive index, absorption coefficient, transmittance and resistivity, but when using general ITO or IZO, the transparent electrode In order to ensure the optical characteristics and electrical characteristics, the thickness is preferably 30 nm or more, more preferably 100 nm or more.

  A protective layer is preferably formed between the organic light emitting layer and the second transparent electrode.

The protective layer is a material capable of injecting or transporting holes and electrons, or both. For example, chromium trioxide (CrO ₃ ), molybdenum trioxide (MoO ₃ ), tungsten trioxide (WO ₃ ), vanadium pentoxide. It is preferably composed of at least one of (V ₂ O ₅ ), niobium pentoxide (Nb ₂ O ₅ ), tantalum pentoxide (Ta ₂ O ₅ ), and magnesium oxide (MgO).

  In addition, a light-transmitting filling layer may be formed between the second transparent electrode and the reflection mirror layer.

  Further, the thickness of the light-transmitting filling layer is not particularly limited to the upper and lower limit values, but is preferably 20 nm or more.

  The reflection mirror layer may be made of a metal material.

  The reflection mirror layer may be composed of a dielectric multilayer film.

  According to still another aspect of the present invention, there is provided a method for manufacturing an organic light emitting device as described above, wherein a glass layer having a light scattering function is formed on a transparent support substrate surface, and the refractive index of the support substrate is greater than or equal to the refractive index. A glass paste composition containing a low melting point glass frit having a refractive index is used to planarize the outermost surface of the glass layer, form a first transparent electrode on the outermost surface of the glass layer, and organically form the first transparent electrode. A light emitting layer is formed, a second transparent electrode is formed so as to form a counter electrode with the first transparent electrode via the organic light emitting layer, and a reflection mirror layer is formed on the outermost surface opposite to the light extraction surface. The manufacturing method of the organic light emitting element containing these is provided.

  Here, a step of forming a protective layer may be further included between forming the organic light emitting layer and forming the second transparent electrode.

  Further, a thin film containing a material having a refractive index higher than that of the first transparent electrode is formed between flattening the outermost surface of the glass layer and forming the first transparent electrode on the outermost surface of the glass layer. Further forming may be included.

  Further, after forming the second transparent electrode, it may further include forming a light transmissive filling layer between the second transparent electrode and the reflection mirror layer.

  Moreover, according to another viewpoint of this invention, a lighting fixture provided with the said organic light emitting element is provided.

  Moreover, according to another viewpoint of this invention, the backlight for display apparatuses provided with the said organic light emitting element is provided.

  Moreover, according to another viewpoint of this invention, a display provided with the said organic light emitting element is provided.

  According to the present invention, since the light emitting portion and the reflective layer are separated by the protective layer, the device characteristics are not deteriorated. In addition, as a method of increasing the distance to the reflective layer, it can be filled with an inert gas, a vacuum, an organic material, or an inorganic material, so that a distance longer than the optical wavelength can be easily ensured.

  Further, according to the present invention, damage to the organic light emitting layer can be reduced by interposing a protective layer, and a transparent electrode is formed by using an ion beam sputtering method, an electron beam plasma deposition method, an electrostatic spray method, or the like. However, since the organic light emitting layer is not damaged, the device characteristics are not deteriorated.

  In addition, according to the present invention, since the light emitting element substrate itself has a light extraction structure, the yield does not decrease.

(A) is explanatory drawing which shows the cross-sectional structure of the conventional bottom emission type OLED, (b) is explanatory drawing which shows the cross-sectional structure of the conventional top emission type OLED. It is explanatory drawing which shows the ratio of the light which is confined in each layer of the conventional OLED, and cannot be taken out, and the light radiated | emitted outside. (A) is explanatory drawing which shows the energy loss by the laminated structure of the conventional OLED, (b) is explanatory drawing which shows the energy loss by the laminated structure of OLED of this invention. It is explanatory drawing which shows the cross-sectional structure of the surface emitting element which concerns on the 1st Embodiment of this invention. It is a graph which shows the result of having calculated at a single interface how much light can be taken out in solid angle conversion, assuming that all the light beyond a critical angle can be taken out. It is explanatory drawing which shows an example of the manufacturing method of the light emitting element substrate of the surface light emitting element which concerns on the same embodiment. It is explanatory drawing which shows an example of the formation method of the high refractive index layer which concerns on the embodiment. It is explanatory drawing which shows the cross-sectional structure of the surface emitting element which concerns on the modification of the 1st Embodiment of this invention. It is explanatory drawing which shows the cross-sectional structure of the surface emitting element which concerns on the 2nd Embodiment of this invention. (A) is explanatory drawing which shows the cross-sectional structure of the surface emitting element which concerns on the 3rd Embodiment of this invention, (b) shows the cross-sectional block diagram of the surface emitting element which concerns on the modification of 3rd Embodiment. It is explanatory drawing. It is explanatory drawing which shows the cross-sectional structure of the surface emitting element which concerns on the 4th Embodiment of this invention.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

[OLED issues]
Before describing a preferred embodiment of the present invention, as a premise thereof, a problem of a general OLED will be described.

(General configuration of OLED)
First, a general configuration of an OLED will be described with reference to FIGS. 1 (a) and 1 (b). FIG. 1A is an explanatory diagram illustrating a general cross-sectional configuration of a bottom emission type OLED, and FIG. 1B is an explanatory diagram illustrating a general cross sectional configuration of a top emission type OLED.

  As shown in FIG. 1A, the bottom emission type OLED 10 is made of a transparent conductive film such as ITO formed on a substrate 11 made of glass or the like by sputtering or resistance heating vapor deposition. The first electrode 12 and N, N′-di (1-naphthyl) -N, N′-diphenylbenzidine (hereinafter abbreviated as NPD) similarly formed on the first electrode 12 by resistance heating vapor deposition or the like. ), A light emitting layer 14 made of 8-hydroxyquinoline Al μmin μm (hereinafter abbreviated as Alq3) formed on the hole transport layer 13 by resistance heating vapor deposition or the like, and a light emitting layer. 14, tris (8-quinolinolato) aluminum, tris (4-methyl-8-quinolinolato) aluminum, bis (2-methyl-8-quinoli) Lat) -4-phenylphenolate-aluminum, electron transport layer 15 made of a metal complex such as bis [2- [2-hydroxyphenyl] benzoxazolate] zinc, and resistance heating vapor deposition method on electron transport layer 15 And a second electrode 16 made of a reflective metal film made of aluminum or the like. When a DC voltage or a DC current is applied with the first electrode 12 of the bottom emission type OLED 10 having the above configuration as a positive electrode and the second electrode 16 as a negative electrode, the first electrode 12 passes through the hole transport layer 13. Then, holes are injected into the light emitting layer 14, and electrons are injected from the second electrode 16 into the light emitting layer 14 through the electron transport layer 15. In the light-emitting layer 14, recombination of holes and electrons occurs, and a light emission phenomenon occurs when excitons generated thereby shift from the excited state to the ground state.

  FIG. 1B is a cross-sectional view showing the structure of the top emission type OLED 20. In the case of the top emission type OLED 20, the bottom emission type OLED 10 in that the first electrode 12 is made of a highly reflective metal layer such as aluminum and the second electrode 16 is made of a transparent conductive film such as ITO. The structure is different. As described above, in the case of a top emission type OLED, the first electrode 12 is generally composed of a reflective metal and the second electrode 16 is composed of a thin film metal or a transparent conductive material. In the case of a bottom emission type OLED, the first electrode 12 is made of a thin film metal or a transparent conductive material, and the second electrode 16 is made of a reflective metal.

  Examples of the transparent conductive material include ITO (Indium Tin Oxide), tin oxide, zinc oxide, IZO (Indium Zinc Oxide), AZO (Aluminum-doped Zinc Oxide), and GZO (Gallium-doped Zinc Oxide). be able to. In addition to the inorganic conductive film, an organic conductive film such as a polyparaphenylene vinylene derivative, a polyfluorene derivative, a polythiophene derivative, or the like can be used as the conductive substance constituting the transparent electrode, or the inorganic conductive film and the A composite film in which an organic conductive film is multilayered can be used.

  However, when the transparent inorganic conductive film is formed using a sputtering method or the like, a significant decrease in light emission is confirmed due to damage to the organic light emitting layer due to collision of secondary electrons such as plasma particles and charged particles.

  In such an OLED 10, light emitted from the phosphor in the light emitting layer 14 is normally emitted in all directions centering on the phosphor, and passes through the hole transport layer 13, the anode 12, and the substrate 11. Radiated into the air. Alternatively, once in the direction opposite to the light extraction direction (the direction of the substrate 11), reflected by the cathode 16, and via the electron transport layer 15, the light emitting layer 14, the hole transport layer 13, the anode 12, and the substrate 11, Radiated into the air. However, when the light passes through the boundary surface of each medium, if the refractive index of the medium on the incident side is larger than the refractive index on the outgoing side, the angle at which the outgoing angle of the refracted wave becomes 90 °, that is, more than the critical angle. Light incident at a large angle cannot pass through the interface, is totally reflected, and light is not extracted into the air.

  The relationship between the light refraction angle and the medium refractive index at the interface between different media generally follows Snell's law. According to Snell's law, when light travels from the medium 1 having the refractive index n1 to the medium 2 having the refractive index n2, the relational expression n1sinθ1 = n2sinθ2 holds between the incident angle θ1 and the refractive angle θ2. In this relational expression, when n1> n2 holds, the incident angle θ1 = Arcsin (n2 / n1) at which θ2 = 90 ° is called a critical angle, and when the incident angle is larger than the critical angle, The light is totally reflected at the interface between the medium 1 and the medium 2. Therefore, in an OLED that emits light isotropically, light emitted at an angle larger than this critical angle repeats total reflection at the interface, is confined inside the device, and is not emitted into the air.

  Here, the light extraction ratio of the bottom emission type OLED as shown in FIG. 1A will be described with reference to FIG. FIG. 2 is an explanatory diagram showing the ratio of light that is confined in each layer of a general OLED and cannot be extracted and light emitted to the outside in a simple calculation using Snell's law. In the example shown in FIG. 2, it is assumed that the hole transport layer and the light emitting layer constituting the OLED have substantially the same refractive index, and n = 1.7 (in FIG. 2, they are collectively shown as an organic thin film layer. ), N = 2.0 when ITO was used as the transparent electrode, and n = 1.5 when a glass substrate was used as the substrate.

  As shown in FIG. 2, the waveguide loss, that is, the light totally reflected between the transparent electrode and the substrate and the light reflected between the organic light emitting layer and the metal electrode interfere with each other and weaken each other, The loss of light that propagates laterally due to the difference in refractive index of the interface (Snell's law) and cannot be extracted from the front is about 30% in total, and the plasmon loss generated on the surface of the reflective metal is about 50%. Thus, it can be seen that only about 20% of the emitted light can be extracted outside.

  As described above, since the light extraction efficiency of the OLED is low, many examples for improving the light extraction efficiency have been proposed. However, in these examples, as described above, the light extraction efficiency is improved to some extent, but there is a problem in terms of mass productivity and ease of manufacture.

  Moreover, when producing surface emitting elements, such as OLED, high smoothness is calculated | required by the surface adjacent to the transparent electrode of a board | substrate. This is because many OLEDs are composed of thin films (several tens of nanometers to several micrometers), and if there are irregularities on the surface of the substrate, current leakage occurs and the element cannot be driven stably. Accordingly, if the surface of the substrate adjacent to the transparent electrode (interface between the transparent conductive film and the substrate) or the transparent electrode itself is not flat, the yield of the manufactured OLED may be reduced, or the lifetime and reliability of the OLED may be reduced. Resulting in.

  By the way, the plasmon loss occurs on the metal surface. This is due to collective excitation of free electrons in the metal. Non-radiative transitions due to excited states in the organic light emitting layer can be reduced by increasing the distance from the recombination region of electrons and holes to the metal surface.

FIG. 3A is an explanatory diagram showing energy loss due to the conventional OLED stack structure, and the “External mode” portion indicates the light extraction rate due to the conventional OLED stack structure. As is apparent from this figure, in the case of a conventional OLED laminated structure, the light intensity distribution of plasmons is maximized on the surface of the reflective metal electrode and monotonously decreases as the distance from the reflective metal electrode increases. Therefore, in order to reduce the plasmon loss, a transparent electrode can be used instead of the reflective metal electrode, or the light emitting point can be separated from the reflective metal electrode. However, the former transparent electrode emits light from the opposite side from the observation direction, so that the light use efficiency is reduced. Since a general transparent electrode is made of a metal oxide material, it directly goes to the organic light emitting layer. It is generally well known that device characteristics are remarkably deteriorated when a film is formed. In the latter case, it is conceivable to increase the thickness of some conventional organic light emitting layer (for example, the electron transport layer), but this is not preferable because the drive voltage increases.
[Outline of the present invention]
Therefore, as a result of intensive studies on means that can solve the above-mentioned problems, the present inventors have obtained the following knowledge and have completed the present invention based on these knowledge.

  That is, according to the present invention, the metal electrode is changed to the protective layer and the transparent electrode, and the plasma loss is achieved by inserting the reflective mirror layer or the light-transmitting filling layer and the reflective mirror layer on the side opposite to the organic light emitting layer. Can be reduced. Also, by combining with a light scattering substrate, light loss that cannot be extracted from the front due to Snell's law can be extracted from the front of the substrate, and a significant improvement in light scattering efficiency can be realized.

  Hereinafter, the present invention made based on the above knowledge will be described in detail with reference to four preferred embodiments. It should be noted that the OLED of the present invention is not limited to the following four embodiments, and may have other structures as long as it includes means obtained by the above-described knowledge. Of course.

[First Embodiment]
[Configuration of OLED 100]
First, the configuration of the OLED according to the first embodiment of the present invention will be described with reference to FIG. FIG. 4 is an explanatory diagram showing a cross-sectional configuration of the OLED 100 according to the first embodiment of the present invention.

  As shown in FIG. 4, the OLED 100 according to the first embodiment of the present invention is a bottom emission type, and includes a support substrate 110, a high refractive index layer 120, a first transparent electrode 130 as a positive electrode, and holes. It mainly includes a transport layer 140, an organic light emitting layer 150, an electron transport layer 160, a second transparent electrode 170 as a cathode, and a reflection mirror layer 180.

  The OLED 100 has an uneven surface 111 formed on the surface of the support substrate 110, and the uneven surface 111 has a structure in which the surface (the surface in contact with the first transparent electrode 130) is flattened by the high refractive index layer 120. doing. Further, in the OLED 100, the high refractive index layer 120 includes the light scattering portion 121 that scatters the light incident from the first transparent electrode 130 side (the uneven surface 111 exists in the region surrounded by the dotted line in FIG. 4). And a flat surface 123 in contact with the first transparent electrode 130, and a single layer having a flat surface 123 in contact with the first transparent electrode 130. Hereinafter, each component of the OLED 100 will be described in detail.

(Supporting substrate 110)
The support substrate 110 is, for example, a substrate formed of a transparent material such as soda lime glass, non-alkali glass, high strain point glass (such as PD200), or transparent plastic, and on one surface thereof, An uneven surface 111 is provided. Examples of the transparent plastic for forming the support substrate 110 include insulative organic materials such as polyethersulfone (PES), polyacrylate (PAR), polyetherimide (PEI), polyethylene naphthalate (PEN). ), Polyethylene terephthalate (PET), polyphenylene sulfide (PPS), polyarylate, polyimide, polycarbonate (PC), cellulose triacetate (TAC), cellulose acetate propionate (CAP), and the like. The concavo-convex surface 111 is a surface having a random concavo-convex that causes disturbance in the refraction angle of incident light when the light generated in the organic light emitting layer 150 passes through the first transparent electrode 130 and enters the support substrate 110. is there. In the present invention, the high refractive index layer 120 is formed on the uneven surface 111 with a flattening material described later. However, the flattening material is a paste material made of glass frit, and it is necessary to melt the glass frit by firing. . Since this baking process is performed at a temperature of about 500 ° C., the support substrate 110 is preferably formed of a glass material having a higher melting point than a plastic material having a lower melting point.

  The degree of unevenness of the uneven surface 111 is not particularly limited, but is preferably 0.7 μm or more and 5 μm or less in terms of the average surface roughness Ra specified in JIS B 0601-2001. When Ra is smaller than 0.7 μm, the light extraction effect may not be sufficient. Moreover, when Ra exceeds 5 μm, the extraction efficiency tends to decrease. The reason is considered as follows. When the light extraction is used to increase the extraction efficiency as in this embodiment, the light is uneven in the OLED 100 in the light scattering portion 121 (the region surrounded by the dotted frame in FIG. 4). Each time it passes through a region near the interface between the support substrate 110 and the high refractive index layer 120 where the surface 111 exists, reflection is repeated many times, and as a result, light can be extracted outside the OLED 100. In consideration of such a mechanism, if Ra is large, the high refractive index layer 120 is inevitably thick in order to flatten. This is because if the thickness of the high refractive index layer 120 having a high refractive index is too thick, loss due to light absorption in the high refractive index layer 120 cannot be ignored. In this respect, the glass frit used as the material of the high refractive index layer 120 used in the present invention is made of a metal oxide and has an extremely small extinction coefficient k in the visible light region. The attenuation of is negligibly small.

  In general, when the surface roughness of a substrate is increased, when used in a display element such as a display, the light is scattered to the outside of each pixel (pixel) due to large light scattering, and blurring occurs. Therefore, although not preferred, a certain degree of unevenness (roughness) is required to increase the light extraction efficiency. When a board | substrate has a large unevenness | corrugation, a device is needed when using it for a display use. Therefore, by optimizing the unevenness of the substrate surface (setting value of Ra) for each application such as display use and illumination or backlight use, it is possible to satisfy each specification and extract light from the front. Become. The support substrate 110 according to the present embodiment assumes a lighting application, and forms the uneven surface 111 having a relatively large Ra.

  The average surface roughness Ra and the maximum roughness Rz described later in this embodiment can be easily measured using a contact-type surface roughness measuring instrument, a non-contact type optical roughness measuring instrument, or the like. Is possible.

  Here, when the uneven surface 111 as described above is provided on the surface of the support substrate 110, light incident on the uneven surface 111 is scattered, so the direction of the light traveling perpendicular to the support substrate 110 is the direction. The ratio of the light transmitted through the support substrate 110 without changing is reduced. Such a state may be expressed as the turbidity (haze value: Haze) of the substrate. Haze is a numerical value (percentage) of the ratio of the transmitted light component that is not perpendicular to the transmitted light that is incident perpendicular to the substrate (the support substrate 110 in this embodiment). A member having a high haze cannot be used for a portion that needs to improve external visibility, such as a window glass, but in order to increase the light extraction efficiency like the structure of the light emitting element substrate of the present embodiment, Thus, it is preferable that there are many components to scatter (non-vertical transmitted light components). From the above viewpoint, the haze of the support substrate 110 is preferably 30% or more, more preferably 50% or more, and further preferably 70% or more. Haze can be easily measured by a commercially available transmissometer with an integrating sphere or a haze meter.

(High refractive index layer 120)
The high refractive index layer 120 is disposed between the support substrate 110 and the first transparent electrode 130 described above, and is a layer having a refractive index equal to or higher than the refractive index of the support substrate 110 and is incident from the first transparent electrode 130 side. It has the light-scattering part 121 which scatters light, and the flat surface 123 which contact | connects the 1st transparent electrode 130. FIG.

  Here, as described above, when a surface light emitting element such as an OLED is formed, high smoothness is required for the light emitting element substrate. Therefore, in this embodiment, in order to flatten the uneven surface 111 formed on the support substrate 110, a glass paste composition containing glass frit is used, and the uneven surface 111 formed on the surface of the support substrate 110 is used. In addition, the high refractive index layer 120 having the flat surface 123 on the side adjacent to the first transparent electrode 130 is provided. As described above, various materials for flattening the unevenness of the substrate surface have been proposed, such as SOG material and CVD film. However, a film thickness that can flatten the unevenness having a large roughness is formed. There are many problems in practical use, such as being unable to perform the process, requiring a very expensive and sophisticated equipment for film formation, and taking time. According to the study by the present inventors, when an SOG material is used, the maximum film thickness that can be formed is at most about 1 to 2 μm, and even a SiN film formed using the CVD method can be practically formed. The film thickness is several μm. The structure (unevenness) for adjusting the refraction angle of the incident light to the substrate, such as light scattering and condensing, is a structure larger than the wavelength of the incident light (unevenness having a roughness larger than the wavelength of the incident light) If the SOG material or the CVD method is used, it is impossible to achieve flattening of the uneven surface.

  On the other hand, in the method using the glass frit of this embodiment, the glass frit is prepared by mixing a high boiling point solvent such as terpineol or butyl carbitol acetate with a thickening binder resin such as ethyl cellulose or acrylic resin. The uneven surface 111 can be easily flattened and the high refractive index layer 120 having a sufficient thickness can be formed simply by applying the glass paste to the support substrate 110, drying and baking. Is possible. The glass paste composition for forming the high refractive index layer 120 is a paste-like composition containing a glass frit, a solvent, and a resin. Hereinafter, each of the glass paste compositions according to the present embodiment will be described. The components will be described.

<Glass frit>
First, the glass frit used in the present embodiment has a thermal characteristic such that a transparent glass layer (high refractive index layer 120) can be formed at a temperature at which the support substrate 110 is not distorted or distorted. There is a need. A general glass substrate (for example, soda lime glass) used as the support substrate 110 is not preferable because a strain or distortion is generated when a temperature of 500 ° C. or higher is applied, and the support substrate 110 is warped. In order to form the high refractive index layer 120 at 500 ° C. or lower, the glass transition temperature (Tg) of the glass frit needs to be 450 ° C. or lower, preferably 400 ° C. or lower.

  Further, if the linear expansion coefficient of the glass frit is different from the linear expansion coefficient of the material forming the support substrate 110, when the high refractive index layer 120 is formed, stress remains in the support substrate 110, causing cracks and the like. Become. Therefore, it is preferable that the linear expansion coefficient of the glass frit in the present embodiment is approximately the same as that of the material (for example, soda lime glass or non-alkali glass) that forms the support substrate 110. For example, in the case of soda lime glass, since the linear expansion coefficient is about 85 × 10 −7 / ° C., a glass frit having a linear expansion coefficient of about (85 ± 10) × 10 −7 / ° C. is preferable. According to the study by the present inventors, if the difference in linear expansion coefficient between the glass frit and the forming material of the support substrate 110 is larger than ± 10 × 10 −7, the film thickness formed by the glass frit is thin. It has been experimentally found that the high refractive index layer 120 may be broken such as cracks.

  The material forming the high refractive index layer 120, that is, the refractive index of the glass frit needs to have a refractive index higher than that of the support substrate 110. The refractive index of the glass frit is preferably about the same as that of the first transparent electrode 130 (for example, formed of ITO). The refractive index of a substrate of a surface light emitting element such as a general OLED is about 1.5, and the refractive index of a transparent conductive film (transparent electrode) is about 2. If the refractive index of the high refractive index layer 120 is approximately the same as that of the support substrate 110, the reflection at the interface with the first transparent electrode 130 is the same as when the irregular surface 111 and the high refractive index layer 120 are not provided. It cannot be desired to improve the light extraction efficiency. Specifically, in the OLED 100 according to the present embodiment, the refractive index of the high refractive index layer 120 is preferably about 1.7 to 2.5. Alternatively, the refractive index nd1 of glass frit for forming the high refractive index layer 120 (d represents 589 nm which is a D line of sodium) and the refractive index nd2 of the first transparent electrode 130 (for example, ITO). The relationship is preferably nd1 / nd2 ≧ 0.9. The reason will be described below.

  As already described, there is a critical angle θ according to Snell's law at the interface between media having different refractive indexes n1 and n2, and this critical angle θ is expressed by θ = Arcsin (n2 / n1). For example, the critical angle of general glass (for example, nd = 1.5) and ITO (for example, nd = 2.0) is 48.6 ° from the above formula, and incident light with an angle less than this critical angle is It is deactivated by being guided through ITO or an organic thin film layer, that is, this incident light cannot be extracted. Here, FIG. 5 is a graph showing the result of calculation at a single interface as to how much light can be extracted in terms of solid angle, assuming that all light above the critical angle can be extracted. The extraction ratio shown on the vertical axis of FIG. 5 is a solid angle 2π of a solid angle (steradian: sr) = 2π (1-cos θ) of an incident angle θ (corresponding to all solid angles when all light can be extracted). The value (1-cos θ) divided by is expressed as a percentage.

  As is apparent from the calculation result shown in FIG. 5, it is understood that the total reflection at the interface is sufficiently small and the total reflection at the interface between the transparent conductive film and the substrate is reduced when nd1 / nd2 ≧ 0.9. . In order to make the influence of total reflection almost zero, it is preferable that nd1 / nd2 ≧ 1. More specifically, for example, when the first transparent electrode 130 formed of ITO having a refractive index nd2 = 2.0 is used, the refractive index nd1 of the high refractive index layer 120 of the present embodiment is 1.8 or more. More preferably, it is 2 or more.

  Examples of the glass frit component having a low glass transition temperature and a high refractive index as described above include, for example, one or more components selected from P2O5, SiO2, B2O3, Ge2O, and TeO2 as a network former. As a high refractive index component, a high refractive index glass containing one or more components selected from TiO2, Nb2O5, WO3, Bi2O3, La2O3, Gd2O3, Y2O3, ZrO2, ZnO, BaO, PbO and Sb2O3 is used. can do. Further, as the glass frit component in this embodiment, in addition to the above components, alkali metal oxides, alkaline earth metal oxides, fluorides, etc. are required for the refractive index in order to adjust the characteristics of the glass. You may use in the range which does not impair the physical property made. Specific examples of the glass frit component system include, for example, B2O3-ZnO-La2O3 system, P2O5-B2O3-R'2O-R "O-TiO2-Nb2O5-WO3-Bi2O3 system, TeO2-ZnO system, and B2O3-Bi2O3 system. , SiO 2 —Bi 2 O 3 system, SiO 2 —ZnO system, B 2 O 3 —ZnO system, P 2 O 5 —ZnO system, etc. Here, R ′ represents an alkali metal element, and R ″ represents an alkaline earth metal element. In addition, the component system mentioned above is only an example, and it is not limited to said example if it is a component system which satisfy | fills conditions, such as the glass transition temperature mentioned above and refractive index. The glass frit material as described above is not particularly limited as long as it has a high refractive index and a low melting point (450 ° C. or lower), but lead-free glass is preferable in view of environmental problems. Further, among high refractive index components, among TiO2, Nb2O5, WO3, Bi2O3, La2O3, Gd2O3, Y2O3, ZrO2, ZnO, BaO, PbO, Sb2O3, on a support substrate 110 having relatively low heat resistance such as soda lime glass. In addition, as an example in which the high refractive index layer 120 can be formed with a low melting point, a material containing Bi2O3 can be preferably used. Preferred glass compositions containing Bi2O3 include, for example, Bi2O3-B2O3-SiO2-ZnO series, Bi2O3-B2O3-SiO2 series, Bi2O3-B2O3-ZnO2 series, Bi2O3-B2O3-R2O-Al2O3 series (R is an alkali metal), etc. Can be mentioned.

<Solvent>
The solvent used in the glass paste composition of the present embodiment is not particularly limited as long as it is an organic solvent. However, considering the production process, if the drying rate is too fast, the organic solvent is dried during production, and solids are precipitated, which is not preferable. From such a point of view, the organic solvent used in the glass paste composition of the present embodiment is preferably a solvent having a boiling point of 150 ° C. or higher, more preferably 180 ° C. or higher. As such a solvent, for example, a terpene solvent (Terpineol etc.), carbitol solvents (butyl carbitol, butyl carbitol acetate) and the like can be used.

<Resin>
The resin used in the glass paste composition of the present embodiment is not particularly limited as long as it develops an appropriate viscosity for coating the paste, but it disappears at a temperature lower than the glass transition temperature of the glass frit. Preferred is a resin. This is because if the resin is not baked and removed at a temperature lower than the temperature at which the glass frit exhibits fluidity, the resin gasifies at the temperature at which the glass is baked, causing bubbles inside the glass. Specific examples that can be suitably used as such a resin include ethyl cellulose and nitrocellulose as cellulosic resins, and acrylic resin and methacrylic resin as acrylic resins.

<Other additives>
If necessary, the glass paste composition of the present embodiment may contain additives for the purpose of improving the dispersibility of the glass frit and the resin and adjusting the rheology. As such an additive, for example, adjustment of viscosity suitable for processes such as slit coating, polymers added for the purpose of improving dispersibility of glass frit, thickeners added for the purpose of rheology adjustment, Examples thereof include a dispersant added for the purpose of preparing a glass paste composition having good dispersibility. Examples of the polymer include acrylic polymers. Examples of the thickener include cellulose resins such as ethyl cellulose, polyoxyalkylene resins such as polyethylene glycol, and the like. Examples of the dispersant include dispersants such as polyvalent carboxylic acids and ammonium salts thereof. Examples of the polyvalent carboxylic acid include lower to higher aliphatic polyvalent carboxylic acids, and these may form an ammonium salt such as a tetrabutylammonium salt. Specifically, for example, the HIPLAAD series manufactured by Enomoto Kasei Co., Ltd., the Disperbyk series manufactured by Big Chemie, and the like can be mentioned. In addition, it is preferable that content of the above additives is 3 mass parts or less with respect to 100 mass parts of glass paste compositions, for example.

<Film thickness>
The thickness of the high refractive index layer 120 is not particularly limited as long as it is sufficient to flatten the uneven surface 111 of the support substrate 110. It is preferable that the thickness is 30 times or more and 40 times or less of the average roughness Ra. The absolute range of the film thickness of the high refractive index layer 120 is preferably about 3 μm or more and 100 μm or less. This is because the maximum height Rz of the uneven surface 111 formed by sandblasting or wet etching is approximately 10 to 20 times Ra as will be described later.

  From the same meaning as described above, the thickness of the high refractive index layer 120 is preferably 1.3 times or more the maximum roughness Rz (described in JIS B 0601-2001) of the uneven surface 111 of the support substrate 110. . This is because if it is less than 1.3 times Rz, the high refractive index layer 120 that provides sufficient reliability with respect to the driving stability described above cannot be obtained.

  As described above, it is impossible to easily form a flattened film having the above thickness with an SOG material (sol-gel material) or a vacuum process (CVD or the like). On the other hand, methods of obtaining a thick planarized film with an organic material such as a polymer are conceivable. However, these methods have sufficient heat resistance (300 ° C.) for forming a transparent conductive film (transparent electrode) such as ITO. In addition, as described above, the high refractive index layer 120 is required to have a high refractive index (preferably 2 or more), but such a refractive index is realized with an organic material. There can be no material that can. That is, unless the glass paste composition containing glass frit in the present embodiment is used, the high refractive index layer 120 having the above thickness cannot be easily formed.

  The film thickness of the high refractive index layer 120 can be confirmed by measuring the film thickness after firing. However, since the support substrate 110 has an uneven surface 111 (uneven structure), depending on the measurement position. Different film thicknesses. Therefore, the film thickness of the high refractive index layer 120 in this embodiment is the thickness from the deepest part of the uneven surface 111 to the uppermost part of the high refractive index layer 120, but the uneven surface 111 is randomly uneven. If it is a shape, it may be difficult to determine the deepest part even by analyzing the cross-sectional shape. In such a case, the film thickness is measured for 10 or more arbitrarily selected sites, There is no problem even if the maximum thickness portion is considered as the film thickness.

<Structure confirmation method, etc.>
Note that, when the uneven surface 111 is flattened, the above-described glass frit needs to be filled in the unevenness (the portion corresponding to the valley of the uneven surface 111) without any gap. Such structures of the support substrate 110 and the high refractive index layer 120 can be easily confirmed by observing the cross-sectional shape using a scanning electron microscope (SEM) or the like.

<Smoothness of the interface between the high refractive index layer 120 and the first transparent electrode 130>
When producing the high refractive index layer 120 having the above-described configuration, by firing the glass paste composition described above under vacuum or pressure, bubbles are generated in the high refractive index layer 120 after firing. It can be remarkably suppressed. More specifically, the number of bubbles existing in the high refractive index layer 120 can be reduced and the size of the bubbles can be reduced by baking under the above-described vacuum or pressure. Thus, by suppressing the generation of bubbles in the high refractive index layer 120, the surface of the high refractive index layer 120 adjacent to the first transparent electrode 130, that is, the high refractive index layer 120 and the first transparent electrode 130, The smoothness of the interface can be significantly improved. Further, since the smoothness of the interface between the high refractive index layer 120 and the first transparent electrode 130 is improved, the manufacturing yield of the OLED 100 is improved and the current leakage is suppressed, so that the lifetime and reliability of the OLED 100 are improved. Also improves. The smoothness required for the interface between the high refractive index layer 120 and the first transparent electrode 130 in the present embodiment is Ra of the surface adjacent to the first transparent electrode 130 of the high refractive index layer 120, which is 30 nm or less. Yes, preferably 1 nm or less.

  Here, in the present embodiment, the above-described haze value (Haze) is used as one index of the degree of suppression of bubble generation in the high refractive index layer 120. That is, the haze value of the high refractive index layer 120 adjacent to the first transparent electrode 130 in the light emitting element substrate for the OLED 100 according to the present embodiment is 5% or less. When the haze value of the high refractive index layer 120 exceeds 5%, the number of bubbles in the high refractive index layer 120 increases, and the size of the bubbles increases. Therefore, the high refractive index layer 120 and the first transparent electrode 130 are increased. Sufficient smoothness at the interface cannot be ensured.

  In addition, although the haze value of the high refractive index layer 120 in this embodiment can be measured with a commercially available transmittance meter with an integrating sphere or a haze meter, the haze value of the high refractive index layer 120 is the light emission of the OLED 100. The haze value of the high refractive index layer 120 alone is used instead of the value of the entire element substrate.

  In the present embodiment, a more direct index using the diameter of the bubbles and the ratio of the bubbles in the high refractive index layer 120 may be used as an index of the degree of suppression of bubble generation in the high refractive index layer 120. . In this case, the diameter of the bubbles present in the high refractive index layer 120 is 1/10 or less, preferably 1/100 or less, of the thickness of the high refractive index layer 120 adjacent to the first transparent electrode 130. Further, the absolute value of the bubble diameter is preferably 5 μm or less, and more preferably 0.5 μm or less.

  Here, the diameter of the bubbles present in the high refractive index layer 120 is the equivalent circle diameter when the bubbles are assumed to be circles, and the field of view when the high refractive index layer 120 is observed using an optical microscope. It is an average value of the diameters of all the bubbles contained in the inside. The thickness of the high refractive index layer 120 is as described above.

  The ratio of the bubbles in the high refractive index layer 120 adjacent to the first transparent electrode 130 is 0.5% or less in terms of the ratio of the area of the horizontal cross section of the bubbles to the total area of the horizontal cross section of the high refractive index layer 120. The ratio of the area of the vertical cross section of the bubble to the total area of the vertical cross section of the high refractive index layer 120 is 0.5% or less. Preferably, the ratio of the bubbles in the high refractive index layer 120 is 0.1% or less as a ratio of the area of the horizontal cross section of the bubbles to the total area of the horizontal cross section of the high refractive index layer 120, and the high refractive index layer 120. The ratio of the area of the vertical cross section of the bubble to the total area of the vertical cross section is 0.1% or less.

  Here, the area of the horizontal (vertical) cross section of the bubble refers to the area of the horizontal (vertical cross section) when the bubble is assumed to be a sphere.

  When the diameter of the bubbles existing in the high refractive index layer 120 and the ratio of the bubbles in the high refractive index layer 120 exceed the above range, the bubbles in the high refractive index layer 120 are separated from the surface of the high refractive index layer 120. The probability of projecting toward the first transparent electrode 130 is increased, and sufficient smoothness at the interface between the high refractive index layer 120 and the first transparent electrode 130 cannot be ensured.

  On the other hand, when the diameter of the bubbles present in the high refractive index layer 120 and the ratio of the bubbles in the high refractive index layer 120 are both within the above range, the interface between the high refractive index layer 120 and the first transparent electrode 130 is smooth. It is preferable because the properties can be further improved.

<Uneven shape of uneven surface 111>
The uneven shape of the uneven surface 111 in the present embodiment may be the random shape described above, or may be a regular shape having a uniform structural unit such as a lens shape or a pyramid shape. . In addition, FIG. 8 is explanatory drawing which shows the cross-sectional structure of OLED100 'which concerns on the modification of this embodiment.

  As shown in FIG. 8, unlike the OLED 100, the OLED 100 ′ has an uneven surface 111 formed on the surface of the support substrate 110 having a uniform structural unit such as a lens shape or a pyramid shape instead of a random shape. . This is because when the OLED according to the present invention is applied to a display application, the irregular surface is not an irregular structure that causes the refraction angle to be disturbed, but a lens structure or pyramid as shown by the irregular surface 111 in FIG. A structure is preferred. In the OLED 100 described above, since the uneven surface 111 has a random structure, light generated in each light emitting layer may be mixed and color bleeding may occur. On the other hand, since the uneven surface 111 has a uniform structural unit as in the OLED 100 ′ according to the present modification, the light generated in the organic light emitting layer 150 can be condensed. As described above, there is no color blur and the light extraction efficiency can be increased efficiently. There are no particular restrictions on the specific shape or size of such a lens structure or pyramid structure, which is sufficiently large for the wavelength range of the generated light and capable of exhibiting a light condensing effect, which is larger than the pixel size. What is necessary is just to have a small structural unit. The pixel size (pixel size) of a general display is about 100 to 600 μm, and each size of RGB is 1/3 of the size, so it is about 30 to 200 μm. Therefore, as a specific shape of the uneven surface 111 in this modification, a lens shape (substantially hemispherical shape) or a pyramid shape (substantially four) having a structural unit with a size (uneven height) of several μm to several tens μm. Pyramid shape).

  Here, FIG. 8 shows an example in which the shape of the concavo-convex surface 111 is a lens structure, but even in the case of a pyramid structure, only the shape of each structural unit is different. This is the same as the structure.

  Further, the film thickness of the high refractive index layer 120 is not particularly limited as long as it is sufficient to flatten the uneven surface 111 of the support substrate 110. It is preferable that the height is not less than 1.3 times the maximum height of the 110 uneven surface 111. That is, if the uneven surface 111 has a lens structure and the structural unit of the lens is a hemispherical shape with a diameter of 10 μm, the maximum height of the uneven surface 111 of the support substrate 110 is 5 μm. The preferable thickness of 120 is 6.5 μm or more. If the lens structural unit is a hemispherical shape having a diameter of 80 μm, the preferable thickness of the high refractive index layer 120 is 52 μm or more.

  Since the other configuration of the OLED 100 ′ is the same as that of the OLED 100 described above, detailed description thereof is omitted here.

(First transparent electrode 130, second transparent electrode 170)
The first transparent electrode 130 is a layer that functions as an anode of the OLED 100, and has a conductivity, and a transparent material is used to extract light out of the OLED 100. The second transparent electrode 170 is a layer that functions as a cathode, and a transparent material is used to transmit the reflected light from the mirror layer 180 and extract the light to the outside of the OLED 100. Specifically, a transparent oxide semiconductor, particularly ITO, IZO (Indium Zinc Oxide), ZnO, In2O3, or the like is preferably used as a material for forming the transparent electrodes 130 and 170, respectively.

(Organic light emitting layer 150)
The organic light emitting layer 150 includes at least a light emitting layer. The organic light emitting layer 150 may include a hole injection layer and an electron injection layer. When the organic light emitting layer 150 includes both the hole transport layer 140 and the hole injection layer, the hole injection layer is disposed closer to the first transparent electrode 130 than the hole transport layer 140. The The organic light emitting layer 150 is disposed on the side farther from the first transparent electrode 130 than the hole transport layer 140.

  As a hole transport material forming the hole transport layer 140, for example, known materials such as α-NPD (NPB), TPD, TACP, and triphenyl tetramer can be used. Moreover, as a hole injection material which forms a hole injection layer, well-known materials, such as polyaniline, a polypyrrole, copper phthalocyanine (CuPc), PEDOT: PSS, can be used, for example.

  The organic light emitting layer 150 may include one or more of red, green and blue light emitting layers.

  Examples of the material for forming the red light emitting layer include tetraphenylnaphthacene (rubrene), tris (1-phenylisoquinoline) iridium (III) (Ir (piq) 3), and bis (2-benzo [b] thiophene. 2-yl-pyridine) (acetylacetonate) iridium (III) (Ir (btp) 2 (acac)), tris (dibenzoylmethane) phenanthroline europium (III) (Eu (dbm) 3 (phen)), tris [4,4′-di-tert-butyl- (2,2 ′)-bipyridine] ruthenium (III) complex (Ru (dtb-bpy) 3 * 2 (PF6)), DCM1, DCM2, Eu (thenoyltrifluoro) Acetone) 3 (Eu (TTA) 3, butyl-6- (1,1,7,7-tetramethyldurori) Le-9-enyl) -4H- pyran) (DCJTB) can be used like, Besides, polyfluorene-based polymer, a polymeric light emitting material, such as polyvinyl-based polymer can be used.

  Examples of the material for forming the green light-emitting layer include Alq3, 3- (2-benzothiazolyl) -7- (diethylamino) coumarin (Coumarin6), 2,3,6,7-tetrahydro-1,1,7, 7, -Tetramethyl-1H, 5H, 11H-10- (2-benzothiazolyl) quinolidine- [9,9a, 1gh] coumarin (C545T), N, N′-dimethyl-quinacridone (DMQA), tris (2-phenyl) Pyridine) iridium (III) (Ir (ppy) 3) can be used, and in addition, polymer light-emitting substances such as polyfluorene-based polymers and polyvinyl-based polymers can also be used.

  Examples of the material for forming the blue light emitting layer include oxadiazole dimer dye (Bis-DAPOXP), spiro compounds (Spiro-DPVBi, Spiro-6P), triarylamine compounds, bis (styryl) amine (DPVBi, DSA), 4,4′-bis (9-ethyl-3-carbazovinylene) -1,1′-biphenyl (BCzVBi), perylene, 2,5,8,11-tetra-tert-butylperylene (TPBe), 9H -Carbazole-3,3 '-(1,4-phenylene-di-2,1-ethene-diyl) bis [9-ethyl- (9C)] (BCzVB), 4,4-bis [4- (di- p-tolylamino) styryl] biphenyl (DPAVBi), 4- (di-p-tolylamino) -4 ′-[(di-p-tolylamino) styri Ru] stilbene (DPAVB), 4,4′-bis [4- (diphenylamino) styryl] biphenyl (BDAVBi), bis (3,5-difluoro-2- (2-pyridyl) phenyl- (2-carboxypyridyl) Iridium III (FIrPic) or the like can be used, and in addition, a polymer light-emitting substance such as a polyfluorene polymer or a polyvinyl polymer can be used.

  As described above, the organic light emitting layer 150 may include the electron transport layer 160 and the electron injection layer in order from the side closer to the second transparent electrode 170 than the light emitting layer. As an electron transport material for forming the electron transport layer 160, known materials such as an oxazole derivative (PBD, OXO-7), a triazole derivative, a boron derivative, a silole derivative, and Alq3 can be used. Moreover, as an electron injection material, well-known materials, such as LiF, Li2O, CaO, CsO, CsF2, can be used, for example.

(Mirror layer 180)
As a material for forming the mirror layer 180, a single element thin film metal of Ag, Pt, Pd, Au, Ni, Ir, Cr, Ag, Mg, Al, Pt, Pd, Au, Ni, Nd, Ir, Compounds having stable properties such as gloss in the air, such as Cr, Li, and Ca oxide compounds and alloys, can be used.

[Manufacturing method of OLED 100]
The configuration of the OLED 100 according to the present embodiment has been described in detail above. Subsequently, the manufacturing method of the OLED 100 according to the present embodiment having the above-described configuration will be described in detail with reference to FIGS. 6 and 7. FIG. 6 is an explanatory diagram showing an example of a method for manufacturing a light emitting element substrate of the OLED 100 according to the present embodiment. FIG. 7 is an explanatory diagram showing an example of a method for forming the high refractive index layer 120 according to the present embodiment.

  Here, the manufacturing method of the light emitting element substrate according to the present embodiment, which is the substrate of the OLED 100, includes a surface roughening step, a coating step, a drying step, and a firing step. The surface roughening step is a step of forming the uneven surface 111 on the surface of the support substrate 110. The coating step is a step of coating a glass paste composition containing a glass frit having a refractive index equal to or higher than that of the support substrate 110, a solvent, and a resin on the surface of the support substrate 110 on which the uneven surface 111 is formed. A drying process is a process of drying the glass paste composition apply | coated to the support substrate 110, and volatilizing a solvent. The baking step is a step of baking the glass paste composition after the solvent has been volatilized under vacuum or pressure to eliminate the resin and remove the resin and melt the glass frit to form the high refractive index layer 120 on the support substrate 110. is there. Hereinafter, a method for manufacturing the OLED 100 including these steps will be described.

(Surface roughening process)
As shown in FIG. 6, on the surface of the support substrate 110 such as soda lime glass or non-alkali glass (see FIG. 6A), by a method such as a sand blast method, a wet etching method (frost method) or a press method, Random uneven surfaces 111 are formed that cause disturbance in the refraction angle of incident light when light generated in the organic light emitting layer 150 passes through the first transparent electrode 130 and enters the support substrate 110 (FIG. 6 ( see b)). The degree of unevenness of the uneven surface 111 formed at this time is not particularly limited as described above, but is preferably 0.7 μm or more and 5 μm or less in terms of average surface roughness Ra.

  Further, when the uneven surface 111 having a uniform structural unit as shown in FIG. 6 is formed, the uneven surface 111 on the surface of the support substrate 110 has a uniform shape such as a lens structure or a pyramid structure. It is formed so as to be uneven with a structural unit. Such a lens structure or pyramid structure can be formed using, for example, a mold thermal transfer method, a photolithography / wet etching method, laser processing, polishing with a grindstone, or the like.

(Preparation of glass paste composition)
Next, a glass paste composition containing the glass frit as described above, a solvent, and a resin is prepared. As a method for preparing this glass paste composition, glass frit, (binder) resin, and other components may be dissolved and mixed in a solvent and then kneaded with a roll mill or the like to produce a paste in which the glass frit is dispersed. The mixing ratio of the glass frit, the solvent and the resin may be, for example, about 70 to 80% by mass of the glass frit, 10 to 20% by mass of the solvent, and about 1 to 2% by mass of the resin. Note that, as described above, in consideration of the melting point of the support substrate 110, it is preferable to carry out a drying step and a baking step described later at a temperature of 500 ° C. or lower. For that purpose, the glass transition temperature of the glass frit is 450 ° C. The following is preferable.

(Coating process)
Next, as shown in FIG. 6, the prepared glass paste composition is coated (applied) on the surface of the uneven surface 111 of the support substrate 110 (see FIG. 6A). The method for applying the glass paste composition is not particularly limited, and for example, a known method such as bar coating, doctor blade, slit coating, or die coating can be used.

(Drying process)
Next, the support substrate 110 with the glass paste composition applied to the uneven surface 111 is transferred to a hot air dryer or the like to remove the solvent (see FIG. 6B). As described above, the drying temperature at this time is preferably 500 ° C. or lower so that the support substrate 110 does not melt. More preferably, it is 100 degreeC or more and 150 degrees C or less.

(Baking process)
After the drying step, the support substrate 110 from which the solvent has been removed is transferred to a baking furnace, and the binder resin is removed by burning at a temperature not lower than the glass transition temperature Tg and not higher than the softening temperature Ts of the glass frit. Is melted (see FIG. 6C). Furthermore, the high refractive index layer 120 is formed on the surface of the support substrate 110 by baking at a temperature not lower than the softening temperature Ts of the glass frit (preferably not higher than 500 ° C.) in a baking furnace (FIG. 6 ( c) and FIG. 7 (d)).

<Principle of vacuum firing and pressure firing>
Here, in this embodiment, the said baking process is performed under a vacuum or pressurization. Thereby, as described above, it is possible to significantly suppress the generation of bubbles in the high refractive index layer 120 after firing. And, by suppressing the generation of bubbles in the high refractive index layer 120, the smoothness of the interface between the high refractive index layer 120 and the transparent electrode 130 is significantly increased, so that the production yield of the OLED 100 is improved, and The lifetime and reliability of the OLED 100 can be improved.

  Here, the principle which can suppress generation | occurrence | production of a bubble by vacuum baking and pressure baking is demonstrated. In the first place, the bubbles in the high refractive index layer 120 exist for the following reason. That is, air is mixed into the glass paste composition from the atmosphere, and air is present around the glass frit. The air remains even after firing, whereby bubbles are generated in the high refractive index layer 120. Thus, after baking the glass paste composition to form the high refractive index layer 120, it is extremely difficult to remove the bubbles generated in the layer. Therefore, as a result of the study by the present inventors, it is sufficient that air does not exist around the glass frit at the time when the glass frit is melted in the firing process. For this purpose, the firing process is performed under vacuum or under pressure. It was found that it should be. In order to prevent air from being present around the glass frit when the glass frit is melted, it is important that the glass frit is in a vacuum or a pressurized state before the glass frit is melted.

<Vacuum firing>
In the case of vacuum firing, since the surroundings of the glass frit at the time of firing are in a vacuum atmosphere, naturally there is almost no air around the glass frit. Therefore, even if the glass paste composition is fired in this state, almost no bubbles are generated in the fired high refractive index layer 120. In order to effectively suppress the generation of bubbles, it is preferable that the glass paste composition is fired under a vacuum of 0.3 Pa or less in the firing step.

<Pressure firing>
In the case of pressure firing, since the glass paste composition is compressed and the glass frit is aggregated during firing, there is almost no air around the glass frit. Therefore, even if the glass paste composition is fired in this state, almost no bubbles are generated in the fired high refractive index layer 120. In order to effectively suppress the generation of bubbles, it is preferable that the glass paste composition is fired under a pressure of 110 kPa or more in the firing step.

  As described above, the high refractive index layer 120 is obtained by coating (coating) the paste composition containing the glass frit described above, followed by drying and baking. If necessary, this operation is repeated a plurality of times. Repeatedly, a desired thickness can be obtained. In particular, when the necessary thickness of the high refractive index layer 120 exceeds 40 to 50 μm, it is preferable to repeat the coating and baking a plurality of times. As described above, in order to improve the light extraction efficiency, it is necessary to increase the maximum height of the unevenness of the support substrate 110. Therefore, in order to flatten such a large unevenness, the high refractive index layer 120 is used. It is necessary to increase the thickness. Therefore, when such large irregularities are formed, the undulations and irregularities on the surface of the support substrate 110 can be made smoother by applying and baking the glass paste composition a plurality of times.

(Formation of transparent electrode 130, organic thin film layer 140, and cathode 150)
Next, a transparent electrode 130 is formed by depositing ITO, IZO, ZnO, In 2 O 3 or the like on the support substrate 110 whose surface is planarized by the high refractive index layer 120 by using a method such as spin coating or sputtering. To do. Furthermore, after forming the hole transport layer 140 and the light emitting layer 150 by vapor-depositing a hole transport material or a light emitting material on the first transparent electrode 130, the electron transport layer 160 and the second transparent electrode 170 are formed, An OLED 100 can be manufactured by depositing a metal such as Ag, Mg, or Al on the second transparent electrode 170 to form a mirror layer 180 (see FIG. 4). In addition, as a formation method of the positive hole transport layer 140, the light emitting layer 150, the electron carrying layer 160, or the mirror layer 180, vacuum deposition, a cast method (spin cast method, dipping method, etc.), an inkjet method, a printing method (letterpress printing, Known methods such as gravure printing, offset printing, and screen printing may be used.

[Uses of OLED100]
The light-emitting element substrate used in the OLED 100 of this embodiment has irregularities (surface roughness) that are equal to or greater than the wavelength order, thereby scattering light incident into the element and efficiently extracting light of all wavelengths. Is possible. Therefore, the OLED 100 can be suitably used as a white OLED or the like, and can be applied to a lighting apparatus or a backlight for a display device that requires high efficiency.

  FIG. 3B shows energy loss due to the stacked structure of the OLED according to the present invention, using the OLED 100 of the present embodiment as an example. According to the laminated structure of the OLED according to the present invention, only the surface plasmon loss (“Surface Plasmon mode”) contributes to the energy loss. In other words, the loss of light energy due to the substrate (“substrate waveguide light loss” “substrate mode”) and the loss of light energy due to the organic layer (“organic layer waveguide light loss”) that has been lost in the conventional stacked structure of OLEDs. "Wavelength mode") can be extracted as light according to the present invention.

[Second Embodiment]
[Configuration of OLED 200]
Next, the configuration of the OLED according to the second embodiment of the present invention will be described with reference to FIG. FIG. 9 is an explanatory diagram showing a cross-sectional configuration of an OLED 200 according to the second embodiment of the present invention.

  As shown in FIG. 9, the OLED 200 according to the second embodiment of the present invention is a top emission type, and includes a reflective mirror layer 280, a support substrate 210, a high refractive index layer 220, and a first transparent as a positive electrode. It mainly includes an electrode 230, a hole transport layer 240, an organic light emitting layer 250, an electron transport layer 260, and a second transparent electrode 270 as a cathode.

  The OLED 200 has a structure in which a concavo-convex surface 211 is formed on the surface of the support substrate 210 and the concavo-convex surface 211 is flattened by the high refractive index layer 220 (surface that contacts the first transparent electrode 230). ing. The high refractive index layer 220 of the OLED 200 includes a light scattering layer 221 having a light scattering portion that scatters light incident from the first transparent electrode 230 side adjacent to the support substrate 210. The light scattering portion in the present embodiment is a region formed within the dotted line in FIG. 9 and a region in the vicinity of the interface between the support substrate 210 and the high refractive index layer 220 where the uneven surface 211 exists. The light scattering layer 221 is a layer having a predetermined thickness including the light scattering portion surrounded by a dotted line in FIG.

  Here, the support substrate 210, the high refractive index layer 220, the first transparent electrode 230, the hole transport layer 240, the organic light emitting layer 250, the electron transport layer 260, the second transparent electrode 270, the mirror layer 280, and the like according to the present embodiment. Regarding the uneven shape of the uneven surface 211, the support substrate 110, the high refractive index layer 120, the first transparent electrode 130, the hole transport layer 140, the organic light emitting layer 150, and the electron transport layer 160 according to the first embodiment described above. The second transparent electrode 170, the mirror layer 180, and the concave and convex surfaces 111 are similar to the concave and convex shapes, and detailed description thereof will be omitted.

  According to the first and second embodiments, an organic light emitting layer exists between the first and second transparent electrodes. As described above, in general, when a non-metallic transparent electrode is formed by sputtering or the like, a significant decrease in light emission is confirmed due to damage to the organic light emitting layer due to collision of plasma particles and secondary electrons (charged particles). Is done. However, it has been found that damage to the organic light-emitting layer can be reduced by a method capable of sublimation deposition of a high melting point material such as ion beam sputtering or electron beam plasma deposition. Further, according to the present invention, plasmon loss can be greatly reduced or suppressed by using transparent electrodes made of metal oxide as the positive electrode and the negative electrode. Therefore, according to the present invention, it is possible to reduce both the waveguide loss and the plasmon loss regardless of the bottom emission type or the top emission type, and as a result, the light utilization efficiency is improved.

[Third Embodiment]
[Configuration of OLED 300]
Next, the configuration of the OLED according to the third embodiment of the present invention will be described with reference to FIG. FIG. 10A is an explanatory diagram showing a cross-sectional configuration of an OLED 300 according to the third embodiment of the present invention.

  As shown in FIG. 10A, the OLED 300 according to the third embodiment of the present invention is a bottom emission type, and includes a support substrate 310, a high refractive index layer 320, and a first transparent electrode 330 as a positive electrode. , Hole transport 340, organic light emitting layer 350, electron transport layer 360, protective layer 361, second transparent electrode 370 as a cathode, and reflection mirror layer 380. Note that the light emitting element substrate according to the present embodiment includes a support substrate 310 and a high refractive index layer 320. The high refractive index layer 320 includes a light scattering layer 321 having a light scattering portion that scatters light incident from the first transparent electrode 330 side adjacent to the support substrate 310.

  Here, the support substrate 310, the high refractive index layer 320, the first transparent electrode 330, the hole transport layer 340, the organic light emitting layer 350, the electron transport layer 360, the second transparent electrode 370, the mirror layer 380, and the like according to the present embodiment. Regarding the uneven shape of the uneven surface 311, the support substrate 110, the high refractive index layer 120, the first transparent electrode 130, the hole transport layer 140, the organic light emitting layer 150, and the electron transport layer 160 according to the first embodiment described above. The second transparent electrode 170, the mirror layer 180, and the concave and convex surfaces 111 are similar to the concave and convex shapes, and detailed description thereof will be omitted. In the present embodiment, the light scattering portion is a region formed within the dotted line in FIG. 10A, and is a region near the interface between the support substrate 310 and the high refractive index layer 320 where the uneven surface 311 exists. The light scattering layer 321 is a layer having a predetermined thickness including the light scattering portion surrounded by a dotted line in FIG.

The OLED 300 according to the third embodiment of the present invention differs from the OLED 100 according to the first embodiment in that it includes a protective layer 361. The protective layer 361 includes chromium trioxide (CrO ₃ ), molybdenum trioxide (MoO ₃ ), tungsten trioxide (WO ₃ ), vanadium pentoxide (V ₂ O ₅ ), niobium pentoxide (Nb ₂ O ₅ ), It is preferably composed of at least one of tantalum pentoxide (Ta ₂ O ₅ ) and magnesium oxide (MgO). However, the protective layer 361 can be formed using an inorganic compound and an organic compound other than the oxide, and a plurality of layers can be formed using an inorganic compound such as the oxide and an organic compound. The protective layer 361 may be formed using a layer.

  In addition, the modification of OLED which concerns on the 3rd Embodiment of this invention is shown in FIG.10 (b). In the embodiment shown in FIG. 10B, a light-transmissive filling layer 390 is provided between the second transparent electrode 370 and the mirror layer 380 of the OLED according to the third embodiment.

  As described above, according to the stacked structure of the OLED according to the present invention, the substrate waveguide light loss and the organic layer waveguide light loss in FIGS. 3A and 3B can be extracted as light according to the present invention. .

  In the example of the conventional OLED laminated structure shown in FIG. 3A, a light extraction rate of about 20% is obtained when the thickness of the light emitting layer is around 50 nm. The remaining 30% moves in the substrate and in the thin film, and 50% is deactivated by surface plasmon resonance or the like.

  On the other hand, in the present invention, the thickness of the transparent electrode on the reflection mirror layer side varies depending on physical properties such as the refractive index, absorption coefficient, transmittance, and resistivity of the transparent electrode itself, but the general thickness varies. When ITO or IZO is used, it is preferably 30 nm or more, more preferably 100 nm or more in order to ensure the function and transparency as an electrode.

  As shown in FIG. 3 (b), when the “total thickness from the light emitting region to the reflecting mirror” is about 100 nm or more, the surface plasmon loss is about 30%. Of these, about 70% can be taken out. Therefore, further improvement in extraction efficiency can be expected by forming a light-transmitting filling layer between the transparent electrode on the reflection mirror layer side and the reflection mirror layer. In the case of the OLED shown in FIG. 10B, the light-transmitting filling layer is formed between the second transparent electrode 370 and the mirror layer 380. The upper limit and the lower limit of the light transmissive filling layer are not particularly limited.

  The light-transmitting filling layer is a light-transmitting substrate, inert gas, vacuum, organic material, inorganic material, or composite material, preferably SiOx, SiNx, MoOx, TiOx, TiOx, WOx, etc. A light-transmitting substance, more preferably a light-transmitting substance having a high refractive index (1.5 to 2.0 or more) can be used.

[Fourth Embodiment]
[Configuration of OLED 400]
Next, the configuration of the OLED according to the fourth embodiment of the present invention will be described with reference to FIG. FIG. 11 is an explanatory diagram showing a cross-sectional configuration of an OLED 400 according to the fourth embodiment of the present invention.

  As shown in FIG. 11, the OLED 400 according to the fourth embodiment of the present invention is a top emission type, and includes a reflective mirror layer 480, a support substrate 410, a high refractive index layer 420, and a first transparent as a positive electrode. It mainly includes an electrode 430, a hole transport 440, an organic light emitting layer 450, an electron transport layer 460, a protective layer 461, and a second transparent electrode 470 as a cathode. The light emitting element substrate according to this embodiment includes a support substrate 410 and a high refractive index layer 420. Further, the high refractive index layer 420 includes a light scattering layer 421 having a light scattering portion that scatters light incident from the first transparent electrode 430 side adjacent to the support substrate 410.

  Here, the support substrate 410, the high refractive index layer 420, the first transparent electrode 430, the hole transport layer 440, the organic light emitting layer 450, the electron transport layer 460, the second transparent electrode 370, the mirror layer 480 according to the present embodiment, Regarding the uneven shape of the uneven surface 411, the support substrate 210, the high refractive index layer 220, the first transparent electrode 230, the hole transport layer 240, the organic light emitting layer 250, and the electron transport layer 260 according to the second embodiment described above. The second transparent electrode 270, the mirror layer 280, and the concave and convex surfaces 211 are the same as the concave and convex shapes, and thus detailed description thereof is omitted. The light scattering portion in the present embodiment is a region formed within the dotted line in FIG. 11, and is a region in the vicinity of the interface between the support substrate 410 and the high refractive index layer 420 where the uneven surface 411 exists. The scattering layer 421 is a layer having a predetermined thickness including the light scattering portion surrounded by a dotted line in FIG.

  The OLED 400 according to the fourth embodiment of the present invention differs from the OLED 100 according to the first embodiment in that it includes a protective layer 461. Since the protective layer 461 can be configured in the same manner as the protective film 361 that configures the OLED 300 according to the third embodiment, a detailed description thereof will be omitted.

  Since the OLED 300 according to the third embodiment and the OLED 400 according to the fourth embodiment include the protective layer, damage can be further suppressed as compared with the OLED 100 according to the first embodiment and the OLED 200 according to the second embodiment. .

  As described above, according to the present invention, plasmon loss can be greatly reduced or suppressed by using a non-metallic material as the first and second transparent electrodes, and a thin film can be obtained by using a light scattering substrate. The light extraction loss in the mode and the substrate mode can be reduced together. Therefore, according to the present invention, it is possible to reduce both the waveguide loss and the plasmon loss regardless of the bottom emission method and the top emission method, and as a result, the light utilization efficiency is improved.

  Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.

(Production of light-emitting element substrate)
First, a light emitting element substrate used as a substrate such as an OLED was manufactured. Specifically, a soda lime glass having a thickness of 0.7 mm and 50 × 50 mm is used as a support substrate, and the surface of the soda lime glass is sprayed with # 800 alumina powder under the condition of 0.5 KPa. A formed support substrate with unevenness (hereinafter referred to as “concave substrate”) was obtained. When the surface of the concavo-convex substrate was observed with a laser microscope VK9510 manufactured by Keyence, concavo-convex portions of Ra = 0.7 um were formed. When measured with a Toyo Seiki haze meter “Haze Guard II”, it was found that the uneven substrate had a transmittance of 82% and a haze value of 91%, and an uneven surface functioning as a light scattering portion was formed.

  Separately, 150 g of Bi2O3-B2O3-ZnO glass frit (particle size distribution D50 = 1.6 μm) having a glass transition temperature Tg = 400 ° C., 3 g of ethyl cellulose STD45 (manufactured by Dow Chemical Co.), 32.9 g of terpineol, butyl carbitol 14.1 g of acetate was dissolved and mixed, and then kneaded with a three roll mill to prepare a glass paste composition.

  The obtained glass paste composition was coated on the concavo-convex substrate and the concavo-convex substrate prepared above (soda lime glass substrate not subjected to sandblasting) using a doctor blade, and the solvent was removed with a hot air dryer at 120 ° C. After removal, transfer to a firing furnace, remove the binder resin by firing at 350 ° C. for 30 minutes, and then fire at 30 ° C. for 30 minutes to form a high refractive index layer, which is a transparent glass layer, on the surface of each substrate did.

  It was 30 micrometers when the film thickness of the high refractive index layer formed on the board | substrate without an unevenness | corrugation was measured with the stylus-type film thickness meter (DEKTAK) by ULVAC. It was found that a glass layer (high refractive index layer) that was colorless and transparent and had a smooth surface was formed. Ra of the substrate on which this high refractive index layer was formed was 30 nm or less.

  Further, the total light transmittance of the substrate fired in the atmosphere (air firing) when forming the high refractive index layer on the substrate without unevenness was 72.2%, and the haze value was 40.2% (Table 1). (1) Refer to Air).

  On the other hand, the total light transmittance of the substrate fired in vacuum (vacuum firing) when forming the high refractive index layer on the substrate without unevenness was 82.3%, and the haze value was 2.66% (Table 1). (2) See Vac.). Table 1 shows the transmittance and haze value of each substrate.

  Moreover, in order to further flatten the outermost surface of the vacuum-baked substrate, a substrate added with a polishing step was also produced.

  Next, 120 nm of ITO was formed on soda lime glass and the three types of glass substrates prepared above using an RF magnetron sputtering apparatus.

[Example]
Using the light emitting element substrate manufactured by the method described above, the OLEDs according to the first to fourth embodiments described above were manufactured as follows.

Example 1
As Example 1, the OLED of the first embodiment having the structure shown in FIG. 4 was produced as follows.

First, an ITO film as a positive electrode is formed on the light scattering substrate prepared as described above by sputtering at 120 nm, followed by cleaning steps such as brush cleaning, ultrasonic cleaning, degreasing, and ultraviolet / ozone cleaning. (Hereinafter referred to as “UV / O ₃ cleaning”). Subsequently, a mono (8-quinolinolato) lithium complex (hereinafter referred to as “Liq”) layer as an electron injection layer, a tris (8-xylinol) aluminum (hereinafter referred to as “Alq ₃ ”) layer as a light emitting layer, and a hole transport layer. A naphthyl-substituted diamine derivative (hereinafter referred to as “α-NPD”) layer was sequentially vacuum deposited. Thereafter, ITO was formed to 100 nm as a cathode and an aluminum (Al) layer was formed to 50 nm as a reflection mirror by sputtering. Finally, by using an ultraviolet curable resin, a sealing plate to which a calcium oxide-based desiccant is attached is attached to the entire laminated structure surface and side surfaces including the light scattering substrate, and the resin is cured by irradiating with ultraviolet rays. The OLED of Example 1 was obtained.

(Example 2)
As Example 2, the OLED of the second embodiment having the structure shown in FIG. 9 was produced as follows.

First, on the light scattering substrate manufactured as described above, an ITO film is sputtered as a positive electrode to form a film having a thickness of 120 nm, and then the back surface of the light scattering substrate, that is, the light scattering substrate on which the positive electrode is not formed. A 50 nm film was formed by sputtering an Al layer as a reflection mirror on the surface side of the film. Thereafter, UV / O ₃ cleaning was performed after cleaning steps such as brush cleaning, ultrasonic cleaning, and degreasing. Subsequently, a Liq layer as an electron injection layer, an Alq ₃ layer as a light emitting layer, and an α-NPD layer as a hole transport layer were sequentially vacuum deposited. Thereafter, ITO was deposited by sputtering with a thickness of 100 nm as a cathode. Finally, by using an ultraviolet curable resin, a sealing plate to which a calcium oxide-based desiccant is attached is attached to the entire laminated structure surface and side surfaces including the light scattering substrate, and the resin is cured by irradiating with ultraviolet rays. An OLED of Example 2 was obtained.

(Example 3)
As Example 3, the OLED of the third embodiment having the structure shown in FIG. 10A was produced as follows.

First, an ITO film as a positive electrode is sputtered on the light scattering substrate prepared as described above to form a film having a thickness of 120 nm, and then cleaning steps such as brush cleaning, ultrasonic cleaning, and degreasing are performed. Further, UV / O ₃ Washed. Subsequently, a Liq layer as an electron injection layer, an Alq ₃ layer as a light emitting layer, an α-NPD layer as a hole transport layer, and a MoO ₃ layer as a protective layer were sequentially vacuum deposited. Thereafter, ITO was formed to 100 nm as a cathode, and an Al layer was formed to 50 nm as a reflection mirror by sputtering. Finally, by using an ultraviolet curable resin, a sealing plate to which a calcium oxide-based desiccant is attached is attached to the entire laminated structure surface and side surfaces including the light scattering substrate, and the resin is cured by irradiating with ultraviolet rays. An OLED of Example 3 was obtained.

(Example 4)
As Example 4, the OLED of the fourth embodiment having the structure shown in FIG. 11 was produced as follows.

First, on the light scattering substrate produced as described above, ITO is sputtered as a positive electrode to form a film having a thickness of 120 nm, and then the back surface of the light scattering substrate, that is, the light scattering substrate on which the positive electrode is not formed. An Al layer was sputtered as a reflection mirror on the surface side to form a film with a thickness of 50 nm. Thereafter, UV / O ₃ cleaning was performed after cleaning steps such as brush cleaning, ultrasonic cleaning, and degreasing. Subsequently, a Liq layer as an electron injection layer, an Alq ₃ layer as a light emitting layer, an α-NPD layer as a hole transport layer, and a MoO ₃ layer as a protective layer were sequentially vacuum deposited. Then, ITO was formed into a film by sputtering as a cathode at 100 nm. Finally, by using an ultraviolet curable resin, a sealing plate to which a calcium oxide-based desiccant is attached is attached to the entire laminated structure surface and side surfaces including the light scattering substrate, and the resin is cured by irradiating with ultraviolet rays. An OLED of Example 4 was obtained.

[Comparative example]
In order to confirm the degree of light extraction efficiency of Examples 1 to 4 described above, the following comparative examples were prepared.

(Comparative Example 1)
A bottom emission type OLED shown in FIG. 1A was produced as Comparative Example 1 as follows. In addition, what was used in Embodiment 1-4 was utilized as a light-scattering board | substrate.

First, an ITO film as a positive electrode is formed on the light scattering substrate produced as described above by sputtering with a thickness of 120 nm, followed by cleaning steps such as brush cleaning, ultrasonic cleaning, and degreasing, and further UV / O ₃ cleaning. Processed. Subsequently, a Liq layer as an electron injection layer, an Alq ₃ layer as a light emitting layer, an α-NPD layer as a hole transport layer, and a MoO ₃ layer as a protective layer were sequentially vacuum deposited. Thereafter, an Al layer was formed as a cathode by vacuum deposition at 70 nm. Finally, by using an ultraviolet curable resin, a sealing plate to which a calcium oxide-based desiccant is attached is attached to the entire laminated structure surface and side surfaces including the light scattering substrate, and the resin is cured by irradiating with ultraviolet rays. A bottom emission type OLED of Comparative Example 1 was obtained.

(Comparative Example 2)
A top emission type OLED shown in FIG. 1B was produced as Comparative Example 2 as follows.

First, on the cleaned glass substrate, an Al layer was sputtered as a reflecting mirror to form a film with a thickness of 50 nm, and an ITO film was sputtered onto the Al layer as a positive electrode to form a film with a thickness of 120 nm. Thereafter, UV / O ₃ cleaning was performed after cleaning steps such as brush cleaning, ultrasonic cleaning, and degreasing. Subsequently, a Liq layer as an electron injection layer, an Alq ₃ layer as a light emitting layer, and an α-NPD layer as a hole transport layer were sequentially vacuum deposited. Thereafter, ITO was deposited by sputtering with a thickness of 100 nm as a cathode. Finally, by using an ultraviolet curable resin, a sealing plate to which a calcium oxide-based desiccant is attached is attached to the entire laminated structure surface and side surfaces including the light scattering substrate, and the resin is cured by irradiating with ultraviolet rays. A top emission type OLED of Comparative Example 2 was obtained.

(Measurement of light extraction efficiency)
For Examples 1 to 4 according to the present invention and Comparative Examples 1 and 2 according to the prior art, current-voltage-luminance characteristics were measured by combining a source meter 2400 from KETHKEY Co. and a Spectra Scan PR600 luminance meter from Photo Research. The take-out efficiency was shown by relative evaluation with the take-out efficiency in Comparative Example 1 being 1. The results are shown in Tables 2 and 3.

  As shown in Table 1, the bottom emission type OLED according to the present invention has a luminance of about 1.4 to 1.6 times that of the bottom emission type OLED of the comparative example. Moreover, the top emission type OLED according to the present invention has a luminance of about 1.3 to 1.6 times that of the top emission type OLED of the comparative example.

  As described above, the OLED according to the present invention includes a first transparent electrode formed between the support substrate and the organic light emitting layer, and a second electrode formed on the organic light emitting layer as a counter electrode of the first transparent electrode. None of the transparent electrodes is made of a highly reflective metal or alloy such as aluminum. The OLED according to the present invention has a structure in which the first transparent electrode or the second transparent electrode is interposed between a reflective mirror layer and the organic light emitting layer. According to Table 1, it is apparent that the light extraction efficiency of the OLED according to the present invention is greatly improved by the structure.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

100, 200, 300, 400 Surface light emitting device 110, 210, 310, 410 Support substrate 111, 211, 311 Uneven surface 120, 220, 320, 420 High refractive index layer 221, 321, 421 Light scattering layer 130, 230, 330 430 First transparent electrode 140, 240, 340, 440 Organic thin film layer 170, 270, 370, 470 Second transparent electrode 180, 280, 380, 480 Reflective mirror layer 390 Light transmissive filling layer

Claims (15)

An organic light-emitting device in which a first transparent electrode, an organic thin film layer, and a second transparent electrode are sequentially stacked on a light-emitting device substrate, and has a reflective mirror layer on the outermost surface opposite to the light extraction surface,
The light emitting element substrate is
A transparent support substrate;
A high refractive index layer having one or more layers disposed between the support substrate and the transparent electrode and having a refractive index greater than or equal to the refractive index of the support substrate;
And the high refractive index layer has a light scattering portion for scattering light incident from the transparent electrode side and a flat surface in contact with the transparent electrode. The diameter of the bubbles present in the high refractive index layer is 1/10 or less of the thickness of the layer adjacent to the transparent electrode among the layers constituting the high refractive index layer,
The ratio of the bubbles in the layer adjacent to the transparent electrode is 0.5% or less as a ratio of the area of the horizontal cross section of the bubbles to the total area of the horizontal cross section of the layer adjacent to the transparent electrode, and the transparent 2. The organic light emitting device according to claim 1, wherein the ratio of the area of the vertical cross section of the bubble to the total area of the vertical cross section of the layer adjacent to the electrode is 0.5% or less.   The organic light emitting device according to claim 1, further comprising a protective layer between the organic thin film layer and the second transparent electrode.   4. The organic light-emitting element according to claim 1, wherein each of the first transparent electrode and the second transparent electrode is made of a metal oxide.   5. The organic light-emitting device according to claim 1, wherein each of the first transparent electrode and the second transparent electrode has a layer thickness of 30 nm or more.   The organic light-emitting device according to claim 1, wherein a light-transmitting filling layer is formed between the second transparent electrode and the reflection mirror layer.   The organic light-emitting element according to claim 1, wherein the reflection mirror layer includes a metal material.   The organic light-emitting element according to claim 1, wherein the reflection mirror layer has a dielectric multilayer film.   A backlight comprising the organic light-emitting device according to claim 1.   A lighting fixture comprising the organic light-emitting device according to claim 1.   A display comprising the organic light-emitting device according to claim 1. It is an organic light emitting element of any one of Claims 1-8,
Form a glass layer having a light scattering function on the transparent support substrate surface,
Flattening the outermost surface of the glass layer using a glass paste composition containing a low melting glass frit having a refractive index equal to or higher than the refractive index of the support substrate;
Forming a first transparent electrode on the outermost surface of the glass layer;
Forming an organic light emitting layer on the first transparent electrode, and forming a second transparent electrode so as to form a counter electrode with the first transparent electrode via the organic light emitting layer;
Forming a reflecting mirror layer on the outermost surface opposite to the light extraction surface;
Manufacturing method of organic light emitting element.   The method of manufacturing an organic light emitting device according to claim 12, further comprising forming a protective layer between forming the organic light emitting layer and forming the second transparent electrode. Method.   A thin film containing a material having a refractive index higher than that of the first transparent electrode is formed between flattening the outermost surface of the glass layer and forming the first transparent electrode on the outermost surface of the glass layer. The method of manufacturing an organic light emitting device according to claim 12, further comprising:   15. The method according to claim 12, further comprising forming a light-transmitting filling layer between the second transparent electrode and the reflection mirror layer after forming the second transparent electrode. The manufacturing method of the organic light emitting element of any one.