WO2013186916A1

WO2013186916A1 - Organic electroluminescence device

Info

Publication number: WO2013186916A1
Application number: PCT/JP2012/065370
Authority: WO
Inventors: 黒田　和男; 秀雄工藤; 浩大畑; 敏治内田
Original assignee: パイオニア株式会社
Priority date: 2012-06-15
Filing date: 2012-06-15
Publication date: 2013-12-19

Abstract

An organic EL device is provided with: an insulating bank that is arranged on a translucent substrate; a translucent electrode that is arranged on the translucent substrate and that is in contact with the bank; an organic layer that is formed on the translucent electrode and that includes a light-emitting layer; and a reflective electrode that is formed on the organic layer. The bank is made from a translucent material having a refractive index that is equal to or less than the refractive index of the translucent electrode and comprises a film of a material having a low refractive index, said film being in contact with the translucent electrode and the translucent substrate. The translucent electrode comprises an uneven side surface that is in contact with the film of a material having a low refractive index and that intersects the main surface of the translucent substrate.

Description

Organic electroluminescence device

The present invention relates to an organic electroluminescence device (hereinafter referred to as an organic EL device) including at least one organic electroluminescence element.

The organic electroluminescence element is configured by, for example, sequentially laminating an organic layer including an anode, a light emitting layer, and a cathode on a transparent glass substrate, and electroluminescence (hereinafter, referred to as “electroluminescence” by injecting current into the organic layer through the anode and the cathode). EL element). The emitted light from the light emitting layer is taken out through the transparent electrode and the substrate by making the electrode on the substrate side transparent. However, since a part of the emitted light from the light emitting layer is trapped and extinguished by total reflection between the transparent electrode-glass interface and between the glass-air interface, about 20% of the light emitted from the light emitting layer is about 20%. Only light can be taken out.

In Patent Document 1, a bank (bank) that partitions an organic layer on a transparent substrate on the light extraction side is made of a transparent material, and a reflection unit that extracts light propagating in the light-transmitting bank to the transparent substrate side in the viewing direction. It discloses a technology that is provided to increase the light extraction efficiency.

Japanese Patent Laid-Open No. 2005-310591

In the technique of Patent Document 1, although light from the light emitting layer in contact with the side surface of the translucent bank is taken out into the bank, there is a problem that light propagating in the bank is attenuated in the bank.

Therefore, in the present invention, providing an organic EL device that can increase the extraction efficiency of light propagating through the transparent electrode is an example of a problem.

The organic EL device of the present invention is an organic EL device having a translucent substrate and at least one organic EL element carried on the translucent substrate,
The organic EL element is formed on the insulating bank disposed on the translucent substrate, the translucent electrode disposed on the translucent substrate and in contact with the bank, and the translucent electrode. An organic layer including a light emitting layer, and a reflective electrode formed on the organic layer,
The bank has a low refractive index material film that is made of a light transmissive material having a low refractive index equal to or lower than the refractive index of the light transmissive electrode and is in contact with the light transmissive electrode and the light transmissive substrate.
The translucent electrode has an uneven side surface that is in contact with the low refractive index material film and intersects the main surface of the translucent substrate.

FIG. 1 is a plan view of an organic EL device according to an embodiment of the present invention. FIG. 2 is a sectional view taken along the line CC in FIG. FIG. 3 is a schematic cross-sectional view schematically showing a laminated structure of the light emitting portion of the organic EL device shown in FIG. FIG. 4 is an enlarged partial sectional view showing a part of the organic EL device shown in FIG. FIG. 5 is a partially enlarged plan view showing adjacent translucent electrodes in the organic EL device shown in FIG. 1 and a low refractive index material film therebetween. FIG. 6 is a partially cutaway perspective view of an organic EL device according to another embodiment of the present invention. FIG. 7 is a partially cutaway perspective view of an organic EL device according to one modification.

Embodiments according to the present invention will be described below with reference to the drawings.

In FIG. 1, an organic EL device OELD includes a plurality of strip-shaped organic EL elements OELE which are partitioned by a plurality of banks BK on a light-transmitting flat substrate 1 such as glass or resin and extend in the y direction. Yes. The plurality of organic EL elements OELE are juxtaposed with each other, for example, exhibiting different emission colors of red light emission R, green light emission G, and blue light emission B. The organic EL elements of RGB emission colors are arranged as a set in the x direction for each set.

As shown in FIG. 2, each of the organic EL elements of the organic EL device is configured by laminating a translucent electrode 2, an organic layer 3 including a light emitting layer, and a reflective electrode 4 on a substrate 1 between banks BK. The This organic EL device is a so-called bottom emission type organic EL panel that takes out light generated in the organic layer 3 from the surface of the substrate 1 by applying a voltage between the translucent electrode 2 and the reflective electrode 4. . The bank BK includes a low refractive index material film LRM that is in contact with the translucent electrode 2 and a bank body BKB formed thereon. The bank body BKB is formed from a dielectric material. The low refractive index material film LRM is formed of a light transmissive dielectric material having a low refractive index equal to or lower than the refractive index of the light transmissive electrode 2. The low refractive index material film LRM has a bottom surface BOM1 that contacts the translucent electrode 2 and a bottom surface BOM2 that contacts the translucent substrate 1. The low-refractive index material film LRM has a film thickness on the translucent electrode 2 that is ¼ or more of the wavelength of the light emitted from the light-emitting layer 3c. This is because the emitted light passes through the low refractive index material film LRM as it is when the wavelength is less than ¼ of the wavelength. In the present specification, “equivalent refractive index” means that the difference between one refractive index and the other refractive index is less than 0.3, preferably 0.2 or less, particularly preferably 0.1 or less. That means. Further, the refractive index “low” or “high” may be “low” or “high” to such an extent that a difference in measurement occurs, but in practice, it exceeds 0.1, preferably exceeds 0.2. More preferably 0.3 or more, still more preferably 0.4 or more, particularly preferably 0.5 or more, indicating a low or high difference.

The plurality of translucent electrodes 2 constituting the anode each have a band shape, extend along the y direction on the substrate 1, and are juxtaposed in parallel with each other at a constant interval in the x direction.

On the edges of the substrate 1 and the translucent electrode 2, a bank BK is formed extending along the y direction so as to cover them. In the bank BK, rectangular openings each extending in the y direction are formed. An organic layer 3 is disposed in each of the openings. The organic layer 3 is juxtaposed in a state of being separated from each other by the bank BK, and partitions a plurality of light emitting regions separated by the bank BK. The bank BK is covered with at least a part of the reflective electrode 4.

As shown in FIG. 3, on the translucent electrode 2 in each opening of the bank BK, as the organic layer 3, a hole injection layer 3a, a hole transport layer 3b, a light emitting layer 3c, an electron transport layer 3d, and an electron The injection layer 3e is laminated in order. The organic layer 3 sandwiched between the translucent electrode 2 and the reflective electrode 4 is a light emitting laminated body, and is not limited to these laminated structures. For example, a hole blocking layer (between the light emitting layer 3c and the electron transporting layer 3d ( For example, a layered structure including at least a light emitting layer or a charge transport layer that can also be used may be used. The organic layer 3 may be configured by omitting the hole transport layer 3b, the hole injection layer 3a, or the hole injection layer 3a and the electron transport layer 3d from the stacked structure. May be.

For example, as the light emitting material of the light emitting layer 3c, any known light emitting material such as a fluorescent material or a phosphorescent material can be applied.

Examples of fluorescent materials that emit blue light include naphthalene, perylene, and pyrene. Examples of fluorescent materials that give green light emission include quinacridone derivatives, coumarin derivatives, and aluminum complexes such as Alq3 (tris (8-hydroxy-quinoline) aluminum). Examples of fluorescent materials that give yellow light include rubrene derivatives. Examples of fluorescent materials that give red light emission include DCM (4- (dicyanomethylene) -2-methyl-6- (p-dimethylaminostyryl) -4H-pyran) compounds, benzopyran derivatives, rhodamine derivatives, and the like. Examples of the phosphorescent material include iridium, platinum, ruthenium, rhodium, and palladium complex compounds. Specific examples of the phosphorescent material include tris (2-phenylpyridine) iridium (so-called Ir (ppy) 3), tris (2-phenylpyridine) ruthenium, and the like.

In this way, the organic layers 3 that emit red, green, and blue emission colors are repeatedly arranged in parallel, and red, green, and blue light are arbitrarily emitted from the surface of the substrate 1 that serves as a light extraction surface. Light that is mixed in proportion and recognized as a single emission color is emitted.

Known methods for forming the organic layer 3 include dry coating methods such as sputtering and vacuum deposition, and wet coating methods such as screen printing, spraying, ink jetting, spin coating, gravure printing, and roll coater. ing. For example, the hole injection layer, the hole transport layer, and the light emitting layer are uniformly formed by a wet coating method, and the electron transport layer and the electron injection layer are sequentially formed uniformly by a dry coating method. A film may be formed. Further, all the functional layers may be sequentially formed in a uniform film thickness by a wet coating method.

The anode translucent electrode 2 for supplying holes to the functional layers up to the light emitting layer 3c includes ITO (Indium-tin-oxide), ZnO, ZnO—Al ₂ O ₃ (so-called AZO), In ₂ O ₃ −. It may be composed of ZnO (so-called IZO), SnO ₂ —Sb ₂ O ₃ (so-called ATO), RuO ₂ or the like. Furthermore, for the translucent electrode 2, it is preferable to select a material having a transmittance of at least 10% at the emission wavelength obtained from the light emitting layer.

The translucent electrode 2 usually has a single-layer structure, but it can also have a laminated structure made of a plurality of materials if desired.

The cathode reflective electrode 4 that supplies electrons to the functional layers up to the light emitting layer 3c is not limited, and for example, metals such as aluminum, silver, copper, nickel, chromium, gold, and platinum are used. In addition, these materials may be used only by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

The material of the reflective electrode 4 preferably includes a metal having a low work function in order to efficiently inject electrons. For example, a suitable metal such as tin, magnesium, indium, calcium, aluminum, silver, or an alloy thereof may be used. Used. Specific examples include low work function alloy electrodes such as magnesium-silver alloy, magnesium-indium alloy, and aluminum-lithium alloy. The silver thin film with a thickness of 20 nm of the reflective electrode 4 has a transmittance of 50%. An Al film having a thickness of 10 nm as the metal thin film has a transmittance of 50%. The 20 nm-thick MgAg alloy film as the metal thin film has a transmittance of 50%. In addition, when the reflective electrode 4 is comprised with a metal thin film, electroconductivity can be ensured if the lower limit of the film thickness is 5 nm.

The reflective electrode 4 can be formed as a single layer film or a multilayer film on the organic layer 3 by sputtering or vacuum deposition.

In this organic EL device, since the organic layer 3 is sandwiched between the translucent electrode 2 and the reflective electrode 4, a driving voltage is applied to the organic layer 3 via the translucent electrode 2 and the reflective electrode 4. Is applied, the light generated in the light emitting layer 3c in the organic layer 3 passes through the translucent electrode 2 and is further reflected by the reflective electrode 4 and then passes through the translucent electrode 2 to transmit the light. It is taken out from the surface of the conductive substrate 1.

[Operation of organic EL device]
Next, the operation of the organic EL device will be described with reference to FIGS. In addition, since the component shown with the same code | symbol as the said Example is the same as that of the organic EL device of the said Example, those detailed description is abbreviate | omitted. In the organic EL device shown in the figure, the refractive index of the glass substrate 1 is n1 = 1.5, the refractive index of the translucent electrode 2 is n2 = 1.8, and the refractive index of the low refractive index material film LRM is n1 = In the following description, it is assumed that the refractive index of the organic layer 3 is equal to or less than the refractive index of the translucent electrode 2.

The translucent electrode 2 in the organic EL device shown in FIG. 4 has an uneven side surface BSS including a group of inclined surfaces that are in contact with the low refractive index material film LRM and intersect the main surface of the substrate 1 between the bank BK and the substrate 1. It has as an end face. The uneven side surface BSS extends zigzag along the longitudinal direction of the bank BK, that is, the y direction. The slope group of the concavo-convex side surface BSS includes a slope that is inclined with respect to the direction perpendicular to the longitudinal direction of the bank BK, that is, the x direction, as a refractive surface.

As shown in FIG. 4, the light L0 emitted from the light emitting layer 3c passes through the translucent electrode 2 (n2 = 1.8). Since there is a difference in refractive index between the translucent electrode 2 and the glass substrate 1 (n1 = 1.5), the first critical angle is θc = arcsin (1.5 / 1.8) here, so that the incident angle ± Light of 56.44 degrees or more is totally reflected, and light L0 of less than ± 56.44 degrees enters the glass substrate 1. Therefore, at the interface between the translucent electrode 2 and the glass substrate 1, the light L1 of ± 56.44 degrees or more is confined between the glass interface of the translucent electrode 2 and the reflective electrode. It should be noted that total reflection also occurs from the glass substrate 1 in the external air layer (refractive index n = 1.0). Here, the second critical angle is θc = arcsin (1.0 / 1.5). Light having an angle of ± 41.8 or more is totally reflected, and light L0 of less than ± 41.8 degrees is emitted from the glass substrate 1.

As shown in FIG. 4, this organic EL device is configured such that light totally reflected at the interface between the transparent electrode 2 and the substrate 1 is totally reflected at the interface of the low refractive index material film LRM. Light L1 having an incident angle greater than or equal to the first critical angle to the glass is totally reflected in the light directed directly from the light emitting point of the light emitting layer 3c to the translucent electrode 2. Therefore, since the totally reflected light L1 has the low refractive index material film LRM below the bank BK, it is totally reflected at the same angle at the interface with the translucent electrode 2 and propagates. The light L1 repeats total reflection between the interface between the low refractive index material film LRM of the translucent electrode 2 and the substrate 1, reaches the uneven side surface BSS of the translucent electrode 2, enters the low refractive index material film LRM, and Propagates to the substrate 1. Since the light L1 enters the low refractive index material film LRM from the concavo-convex side surface BSS of the translucent electrode 2, it enters the substrate 1 with the second critical angle standing. Therefore, as shown in FIG. 4, the angle at which the light at the end face of the translucent electrode 2 is extracted to the external air layer can be changed.

FIG. 5 is a partially enlarged plan view showing adjacent translucent electrodes 2 of this organic EL device and a low refractive index material film LRM therebetween. As shown in FIG. 5, the concavo-convex side surface BSS extends in a zigzag along the longitudinal direction of the bank BK, that is, the y direction, that is, includes a plurality of refractive surfaces having different inclination angles with respect to the x direction. The propagating light L1 is deflected by being deflected in the y direction by the refracting surface.

FIG. 6 is a perspective view showing the periphery of the bank BK by partially cutting away the organic EL device of another embodiment. As shown in FIG. 6, only the angles and orientations of the inclined surfaces of the concavo-convex side surface BSS formed of the inclined group of the translucent electrode 2 are randomly configured, and the other configurations are the same as those in the above embodiment. . By making the uneven side surface BSS a random inclined surface, the emitted light from the uneven side surface BSS of the translucent electrode 2 can be refracted in various directions. That is, of the light confined in the translucent electrode 2, the light hitting the interface of the low refractive index material film LRM enters the low refractive index material film LRM at a different angle. In addition, as shown in FIG. 5, you may set the uneven | corrugated side surface BSS by changing the angle of each refractive surface and its direction periodically in ay direction.

As shown in FIGS. 5 and 6, the uneven side surfaces BSS of the adjacent translucent electrodes 2 are each formed by arranging a plurality of refracting surfaces in the longitudinal direction (y direction). Each refracting surface is an end surface that intersects at various angles in the xy plane where the translucent electrode 2 extends. Thereby, the bottom surface BOM reflects the light from the light emitting layer 3c in various directions. In other words, the translucent electrode 2 portion under the bank is provided with an uneven groove composed of a plurality of planes. This is because a straight groove extending in the longitudinal direction of the bank BK makes it difficult to take out light rays that are parallel or nearly parallel to the groove, and a large amount of light is transmitted to the low refractive index material film LRM between the concave and convex grooves. This is because the electrode propagation light is scattered.

According to the present embodiment, the translucent bank BK can change the traveling direction of the light to the light extraction surface to the low refractive index material film LRM4 in various ways and has low refraction in contact with the organic layer 3. Light emitted from the bank interface of the refractive index material film LRM can be taken into the translucent electrode 2 through the low refractive index material film LRM.

In the present embodiment, the concave and convex groove shape can be changed by patterning the translucent electrode 2, and therefore, it can be easily formed only by changing the mask shape.

Conventionally, a large amount of propagating light from the translucent electrode is absorbed when entering the bank BK, so that the light extraction efficiency is lowered. In this embodiment, however, the uneven side surface that refracts the light entering the translucent electrode 2 in various directions. BSS is provided. As a result, the light extraction efficiency can be improved and the light is refracted to the adjacent light emitting area, so that the non-light emitting portion between the colors can be made inconspicuous. That is, in this embodiment, the light transmissive electrode 2 is arranged so that the light totally reflected at the interface between the light extraction side light transmissive substrate 1 and the low refractive index material film LRM is not easily absorbed by the bank BK of the non-light emitting portion. Is provided with an uneven side surface BSS.

[Modification]
FIG. 7 is a perspective view showing the periphery of the bank BK by partially cutting away the organic EL device of the modification. In addition, since the component shown with the same code | symbol as the said Example is the same as that of the organic EL device of the said Example, those detailed description is abbreviate | omitted. In the above-described embodiment, the uneven side surface BSS of the translucent electrode 2 under the bank BK is configured as a zigzag inclined surface connected as a plurality of inclined surface groups. It is comprised by the inner surface of each of several through-holes. The propagation light in the translucent electrode 2 may be scattered by the uneven side surface BSSy, and the end surface of the translucent electrode 2 may not be continuous. In this modification, a plurality of through holes are provided in place of the zigzag grooves separating the two light emitting units between the adjacent light emitting units, so that the light transmissive electrodes 2 are common to the adjacent light emitting units. Therefore, the reflective electrode 4 on the bank BK is separated by providing a slit to prevent a short circuit between adjacent light emitting portions. As described above, in the organic EL device in which the cathode reflective electrode 4 is separated by the adjacent light emitting portion and the anode translucent electrode 2 is integrated, a hole is formed in the translucent electrode 2 so that the uneven side surface BSSy is formed. May be provided.

Further, the plurality of slope groups on the uneven side surface BSS of the translucent electrode 2 may scatter the propagation light in the translucent electrode 2, and for example, the normal direction of the slope group is distributed in a three-dimensional direction. May be formed.

In any of the above embodiments, in the organic EL device, a low refractive index material is used as a material on the light extraction side of a non-light-emitting area such as a bank, and the light-transmitting electrode 2 in contact with the non-light-emitting area is used. A concave / convex side surface BSSy is formed by opening a gap between a through-hole or a hole. Thus, by filling the gap with the low refractive index material, if the light totally reflected by the translucent electrode 2 part enters the gap part through the uneven side surface BSSy, the refraction angle changes and the substrate 1 can be emitted at various radiation angles, and the light extraction efficiency of light propagating through the transparent electrode can be increased.

As the translucent substrate 1, a quartz or glass plate, a metal plate or a metal foil, a resin substrate that can be bent, a plastic film, a sheet, or the like is used. In particular, a glass plate or a transparent plate made of a synthetic resin such as polyester, polymethacrylate, polycarbonate, or polysulfone is preferable. When using a synthetic resin substrate, it is necessary to pay attention to gas barrier properties. If the gas barrier property of the substrate is too small, the organic EL device may be deteriorated by outside air that has passed through the substrate, which is not preferable. Therefore, a method of securing a gas barrier property by providing a dense silicon oxide film or the like on at least one surface of the synthetic resin substrate is also a preferable method.

Further, a sealing can (not shown) for covering and sealing the light emitting portions juxtaposed in a strip shape of the organic EL device and the surrounding banks may be provided. Furthermore, in order to increase the output light extraction efficiency, a light extraction film (not shown) may be attached to the outer surface of the substrate 1 so as to cover the light emitting portion.

Furthermore, in any of the above-described embodiments, the organic layer is a light emitting laminate, but the light emitting laminate can also be configured by laminating inorganic material films.

DESCRIPTION OF SYMBOLS 1 Substrate 2 Translucent electrode 3 Organic layer 3a Hole injection layer 3b Hole transport layer 3c Light emitting layer 3d Electron transport layer 3e Electron injection layer 4 Reflective electrode BK Bank BOM Bottom surface LRM Low refractive index material film

Claims

An organic EL device having a translucent substrate and at least one organic EL element carried on the translucent substrate,
The organic EL element includes an organic layer including at least one insulating bank disposed on the translucent substrate, a translucent electrode in contact with the bank, and a light emitting layer formed on the translucent electrode. And a reflective electrode formed on the organic layer,
The bank has a low refractive index material film that is made of a light transmissive material having a low refractive index equal to or lower than the refractive index of the light transmissive electrode and is in contact with the light transmissive electrode and the light transmissive substrate.
The organic EL device, wherein the translucent electrode has a concavo-convex side surface in contact with the low refractive index material film and intersecting with a main surface of the translucent substrate.
2. The organic EL device according to claim 1, wherein the uneven side surface includes a group of slopes inclined with respect to a direction perpendicular to a longitudinal direction of the bank.
3. The organic EL device according to claim 2, wherein the uneven side surface extends along a longitudinal direction of the bank.
The organic EL device according to claim 2, wherein the uneven side surface is an inner side surface of a hole penetrating the translucent electrode.
2. The organic EL device according to claim 1, wherein the low refractive index material film has a film thickness of ¼ or more of the wavelength of the light emitted from the light emitting layer on the translucent electrode.