JP2007207509A - Organic electroluminescent element and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance light extraction efficiency and reduce visual field angle dependency. <P>SOLUTION: The organic electroluminescent element, provided with a light extraction-side electrode 2, a reflecting electrode 8, and organic laminated films 3 to 7 containing light-emitting layers 5a, 5b arranged between the light extraction-side electrode 2 and the reflecting electrode 8, has ruggednesses formed with a surface roughness Ra equivalent to 4 nm or more on an interface between the light extraction-side electrode 2 and the organic laminated films 3 to 7. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an organic electroluminescence element (organic EL element) and a method for producing the same.

  In recent years, with the diversification of information equipment, development of a display using an organic EL element is expected as a flat display element that consumes less power than a CRT that has been generally used. Further, the organic EL element is also expected as a pollution-free (mercury-less) lighting device that replaces a fluorescent lamp or the like.

  An organic EL element is a self-luminous element utilizing the principle that a fluorescent substance emits light by recombination energy of holes injected from an anode and electrons injected from a cathode by applying an electric field. C. W. Since the report of the low-voltage drive organic EL element by Tang et al. (Non-Patent Document 1) has been made, research on organic EL elements using organic materials as constituent materials has been actively conducted. Tang et al. Use tris (8-quinolinol) aluminum for the light emitting layer and a triphenyldiamine derivative for the hole transporting layer. The advantages of the stacked structure are that it increases the efficiency of hole injection into the light-emitting layer, increases the efficiency of excitons generated by recombination by blocking electrons injected from the cathode, and the excitation generated in the light-emitting layer For example, confining a child. As in this example, the element structure of the organic EL element includes a hole transport (injection) layer, a two-layer type of electron transporting light emitting layer, or a hole transport (injection) layer, light emitting layer, and electron transport (injection) layer. Layered types are well known. In such a multilayer structure element, the element structure and the formation method have been devised in order to increase the recombination efficiency between injected holes and electrons.

  However, in an organic EL element, the probability of singlet generation is limited due to the dependence of spin statistics upon carrier recombination, and therefore an upper limit is imposed on the light emission probability. It is known that the upper limit value is approximately 25%. Furthermore, in a surface light emitting device such as an organic EL device, light having an emission angle greater than the critical angle is totally reflected and cannot be extracted outside due to the influence of the refractive index of the light emitter. For this reason, if the refractive index of the light emission efficiency is 1.6, it is estimated that only about 20% of the total light emission amount can be effectively used. For this reason, as the limit of the energy conversion efficiency, the singlet generation probability is combined and the total efficiency is about 5%.

  In recent years, the use of triplet light-emitting materials as light-emitting materials has improved energy efficiency by a factor of three, but the low light extraction efficiency (20%) is a major factor leading to a decrease in the efficiency of organic EL devices. It has become. As a method for improving the light extraction efficiency, for example, a method for improving the efficiency by providing the substrate with a light condensing property (Patent Document 1) or a method for forming a reflective surface on the side surface of the element (Patent Document 2). Has been proposed. In addition, a method (Patent Document 3) is proposed in which a flat layer having an intermediate refractive index is introduced between a substrate glass and a light emitter to form an antireflection film.

  In Patent Document 4, adjacent to a pixel used in an organic electroluminescence device, a white particle in a transparent polymer or a partition in which transparent fine particles having a refractive index different from that of a polymer are dispersed on a substrate. An organic electroluminescence device provided as an optical waveguide is disclosed.

  In Patent Document 5, an organic electroluminescence device including an anode for injecting holes, a light emitting layer having a light emitting region, and a cathode for injecting electrons is described, and at least one of these electrodes is A configuration is described in which the light-transmitting electrode has means for converting the angle of light emitted from the light-emitting layer inside the light-transmitting electrode.

  Patent Document 6 describes one or a plurality of organic electroluminescence light-emitting elements that are provided on one side of a substrate, directly or via an underlayer, including a substrate and a plurality of light conversion means, A plurality of light angle conversion means are provided for each of the one or a plurality of organic electroluminescence light emitting elements. In this publication, the light angle conversion means is disclosed as a configuration in which the longitudinal direction of the outer shape of a transparent substance, opaque particles, or air layer is oriented in the thickness direction of the substrate. In addition, it has been proposed to improve the light extraction efficiency by providing a photonic crystal, a diffraction grating, or the like (Patent Documents 7 to 9 and the like).

  However, the above-described conventional method has the following problems. The method of improving the light extraction efficiency by giving the substrate a light condensing property and the method of forming a reflective surface on the side surface of the element are effective for elements having a large light emitting area. In a device with a small pixel area such as a lens, it is very difficult to form a lens for condensing light, a reflecting surface on a side surface, or the like. Furthermore, in the organic EL element, since the film thickness of the light emitting layer is several μm or less, it is difficult to form a reflecting mirror on the side surface of the element by applying a taper process, and A significant cost increase is brought about.

  On the other hand, the method of forming an antireflection film by introducing a flat layer having an intermediate refractive index between the substrate glass and the light emitter is effective in improving the light extraction efficiency to the front. It is difficult to prevent. Therefore, even if it is effective for an inorganic electroluminescent element having a large refractive index, it cannot provide a significant improvement effect of light extraction efficiency for an organic EL element that is a light emitter having a relatively low refractive index.

  In general, propagating light traveling in the organic EL element toward the metal electrode (cathode) surface is subjected to a large propagation loss by the metal electrode. For this reason, in order to extract this propagation light efficiently, it is necessary to arrange | position a partition with a short space | interval. Therefore, in the method disclosed in Patent Document 4, the area of the light emitting portion of the element is reduced, and a large improvement effect cannot be achieved.

  Further, in the method disclosed in Patent Document 5, since the area of a place where an electric field cannot be applied increases, a large improvement effect cannot be expected as described above.

  Furthermore, the method disclosed in Patent Document 6 cannot efficiently extract light emitted at a high angle equal to or higher than the critical angle. Further, in the method disclosed in Patent Document 6, it is described that the performance is improved by providing the light angle conversion means throughout the substrate. However, if there are many scattering means in the thickness direction of the substrate, the substrate is Whitening occurs, causing a problem that the color purity of the emitted light is lowered.

  Further, Patent Document 7 and the like have the following problems. That is, when a photonic crystal is used, the emitted light can be efficiently extracted, but the obtained light emission has high directivity, and when used in a display, when viewed obliquely, the luminance is decreased and the chromaticity change is large. The problem of becoming. Also, fine processing is required for photonic crystals and diffraction gratings, resulting in a significant cost increase.

As described above, the conventional method has not yet sufficiently improved the light extraction of the organic EL element.
JP-A-63-314795 JP 2004-119211 A Japanese Patent Laid-Open No. 62-172691 JP 2002-260844 A JP 2002-260866 A JP 2002-260845 A JP 2004-30964 A JP-A-2005-251525 JP 2003-115377 A C. W. Tang, S. A. VanSlyke, ApplIedPhysIcsLetters), 51, 913, 1987

  An object of the present invention is to provide an organic EL element capable of increasing light extraction efficiency and reducing viewing angle dependency and a method for manufacturing the same.

  The organic EL device of the present invention is an organic electroluminescence device comprising a light extraction side electrode, a reflection electrode, and an organic laminated film including a light emitting layer disposed between the light extraction side electrode and the reflection electrode, An unevenness corresponding to a surface roughness Ra of 4 nm or more is formed at the interface between the extraction-side electrode and the organic laminated film.

  In the present invention, irregularities corresponding to a surface roughness Ra of 4 nm or more are formed at the interface between the light extraction side electrode and the organic laminated film. For this reason, when the light emitted from the light emitting layer in the organic laminated film passes through the light extraction side electrode and is emitted to the outside, the ratio of the light totally reflected at the interface between the light extraction side electrode and the organic laminated film is reduced. This can increase the light extraction efficiency. In addition, since the unevenness is formed at the interface between the light extraction side electrode and the organic laminated film, the direction in which the light is emitted can be dispersed, and the viewing angle dependency can be reduced.

  In the organic EL element, the factor that reduces the light extraction efficiency is that light is reflected by total reflection occurring at the interface between the layers depending on the refractive index difference between the light extraction side electrode, the organic laminated film, and the substrate material. It is considered to be trapped. When the refractive index of the organic laminated film, light extraction side electrode (transparent conductive material such as ITO and IZO), and substrate glass is 1.7, 2.0, and 1.5, respectively, confinement in each layer by total reflection The ratio of the light energy to be obtained is estimated to be 47% in the thin film layers such as the organic laminated film and the light extraction side electrode, and 34% in the glass substrate. Therefore, the loss in the thin film occupies a considerable weight, and the light extraction efficiency can be greatly improved by improving the loss in the thin film. In the present invention, irregularities corresponding to a surface roughness Ra of 4 nm or more are formed at the interface between the light extraction side electrode and the organic laminated film. By forming such irregularities at the interface, the light extraction side electrode and the organic laminated film are formed. Total reflection at the interface of the film can be reduced, and light extraction efficiency can be improved.

  In addition, when light emitted from the interface between the light extraction side electrode and the organic laminated film is incident on the substrate, the incident angle with respect to the substrate is also changed to various angles. Loss due to reflection is also reduced, and the light extraction efficiency is further increased.

  The organic EL device according to the first aspect of the present invention is a bottom emission type organic EL device, in which a light extraction side electrode made of a transparent conductive film is provided on a substrate, and an organic layer is formed on the light extraction side electrode. A laminated film is provided, and a reflective electrode is provided on the organic laminated film.

  The organic EL element of the first aspect is a bottom emission type, and light emitted from the light emitting layer is emitted from the substrate side to the outside through the interface between the light extraction side electrode and the organic laminated film.

  The organic EL device according to the first aspect has, for example, a step of forming a light extraction side electrode made of a transparent conductive film on a substrate, and etching the surface of the light extraction side electrode, thereby providing unevenness with a surface roughness Ra of 4 nm or more. It can be manufactured by a manufacturing method including a step of forming and a step of sequentially forming an organic laminated film and a reflective electrode on the light extraction side electrode.

  A transparent conductive film formed from a conductive transparent metal oxide such as indium-tin oxide (ITO) or indium-zinc oxide (IZO) is etched by contacting the surface with an acid or alkali solution, for example. can do. The degree of unevenness formed by etching can be appropriately adjusted by controlling the type, concentration, treatment time, etc. of the acid or alkali solution used. By forming irregularities by etching, irregularities with random shapes are formed on the surface of the transparent conductive film.

  Corresponding to the surface roughness of the transparent conductive film at the interface between the light extraction side electrode and the organic laminated film by providing the organic laminated film on the light extraction side electrode made of the transparent conductive film having a surface with unevenness. Unevenness can be formed. The surface roughness Ra can be measured by, for example, an atomic force microscope (AFM).

  Further, in the first aspect, the organic laminated film and the reflective electrode are sequentially formed on the light extraction side electrode on which the unevenness is formed. Generally, the thickness of each layer in the organic laminated film is very thin. Therefore, irregularities corresponding to the irregularities on the surface of the light extraction side electrode are also taken over at the interface in the organic multilayer film and at the interface between the organic multilayer film and the reflective electrode. In this case, irregularities are also formed on the reflective surface of the reflective electrode, which is considered to contribute to the improvement of light extraction efficiency.

  A second aspect of the present invention is a top emission type organic EL element, in which a reflective electrode is provided on a substrate, a transparent conductive film is provided on the reflective electrode, An organic laminated film is provided thereon, a light extraction side electrode is provided on the organic laminated film, and irregularities corresponding to a surface roughness Ra of 4 nm or more are formed at the interface between the transparent conductive film and the organic laminated film. By taking over the irregularities, irregularities corresponding to a surface roughness Ra of 4 nm or more are formed at the interface between the organic laminated film and the light extraction side electrode.

  In the second aspect of the present invention, an unevenness corresponding to a surface roughness Ra of 4 nm or more is formed at the interface between the transparent conductive film and the organic stacked film, and the organic stacked film positioned above the unevenness is inherited. And irregularities corresponding to a surface roughness Ra of 4 nm or more are formed at the interface between the electrode and the light extraction side electrode. Also in the second aspect, for the same reason as described above, the light extraction efficiency can be increased, and the viewing angle dependency can be reduced.

  The organic EL device according to the second aspect of the present invention includes, for example, a step of forming a reflective electrode on a substrate, a step of forming a transparent conductive film on the reflective electrode, and etching the surface of the transparent conductive film to form a surface. It can be manufactured by a manufacturing method including a step of forming irregularities with a roughness Ra of 4 nm or more and a step of sequentially forming an organic laminated film and a light extraction side electrode on the transparent conductive film.

  Etching of the transparent conductive film can be performed in the same manner as described above.

  The organic EL device according to the third aspect of the present invention is a top emission type organic EL device, in which a first transparent conductive film is provided on a substrate, and a reflective electrode is provided on the first transparent conductive film. The second transparent conductive film is provided on the reflective electrode, the organic laminated film is provided on the second transparent conductive film, and the light extraction side is provided on the organic laminated film. An electrode is provided, and irregularities corresponding to a surface roughness Ra of 4 nm or more are formed at the interface between the first transparent conductive film and the reflective electrode. By taking over the irregularities, the organic laminated film and the light extraction side electrode Unevenness corresponding to a surface roughness Ra of 4 nm or more is formed on the interface.

  In the third aspect of the present invention, a first transparent conductive film is formed as a base layer of the reflective electrode, an unevenness is formed at the interface between the first transparent conductive film and the reflective electrode, and the unevenness is taken over. Thus, irregularities corresponding to a predetermined surface roughness Ra are formed at the interface between the organic laminated film and the light extraction side electrode. Also in the organic EL element according to the third aspect, the light extraction efficiency can be increased for the same reason as described above, and the viewing angle dependency can be reduced.

  The organic EL device according to the third aspect of the present invention includes, for example, a step of forming a first transparent conductive film on a substrate and a surface roughness Ra of 4 nm or more by etching the surface of the first transparent conductive film. And a step of sequentially forming a reflective electrode, a second transparent conductive film, an organic laminated film, and a light extraction side electrode on the first transparent conductive film. it can.

  In the organic EL element according to the third aspect, irregularities can also be formed on the reflective surface of the reflective electrode, and the reflection angle of light reflected by the surface of the reflective electrode can be changed to various angles. Furthermore, the light extraction efficiency can be increased and the viewing angle dependency can be reduced.

  As described above, in the present invention, by forming irregularities corresponding to the surface roughness Ra of 4 nm or more at the interface between the light extraction side electrode and the organic laminated film, the light extraction efficiency is increased and the viewing angle dependency is reduced. Yes. The surface roughness Ra is preferably in the range of 4 to 30 nm, more preferably in the range of 4 to 25 nm. When the value of the surface roughness Ra is small, the effects of the present invention that increase the light extraction efficiency and reduce the viewing angle dependency may not be sufficiently obtained. Further, if the value of the surface roughness Ra is excessively large, a uniform thin film cannot be formed in a thin layer such as an organic laminated film, and the light emission characteristics may be deteriorated. In some cases, the light is shorted and cannot emit light. Moreover, it is preferable that the inclination | tilt angle of an unevenness | corrugation is 60 degrees or less.

  In the present invention, examples of the layer constituting the organic laminated film include a hole injection layer, a hole transport layer, an electron transport layer, and an electron injection layer in addition to the light emitting layer. The film thickness of each layer in the organic laminated film is preferably larger than the height of the unevenness formed at the interface between the light extraction side electrode and the organic laminated film.

  According to the present invention, the light extraction efficiency can be increased and the viewing angle dependency can be reduced.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to a following example.

  FIG. 1 is a schematic cross section showing an organic EL device according to a first embodiment of the present invention. The organic EL element shown in FIG. 1 is a bottom emission type organic EL element.

As shown in FIG. 1, a laminated film 11 of, for example, a layer made of silicon oxide (SiO ₂ ) and a layer made of silicon nitride (SiN _x ) is formed on a transparent substrate 1 made of glass or plastic. ing.

  A plurality of TFTs (thin film transistors) 20 are formed on the laminated film 11 so as to correspond to the red region R, the green region G, and the blue region B. Each TFT 20 includes a channel region 12, a drain electrode 13 d, a source electrode 13 s, a gate oxide film 14, and a gate electrode 15.

  A channel region 12 made of, for example, a polysilicon layer is formed in a partial region on the stacked film 11. A drain electrode 13 d and a source electrode 13 s are formed on the channel region 12. A gate oxide film 14 is formed on the channel region 12. A gate electrode 15 is formed on the gate oxide film 14. A drain electrode 13d of each TFT 20 is connected to a hole injection electrode 2 described later, and a source electrode 13s of each TFT 20 is connected to a power supply line (not shown).

  A first interlayer film 16 is formed on the gate oxide film 14 so as to cover the gate electrode 15. A second interlayer film 17 is formed on the first interlayer insulating film 16 so as to cover the drain electrode 13d and the source electrode 13s. The gate electrode 15 is connected to a signal line (not shown). The gate oxide film 14 has a laminated structure of a layer made of, for example, silicon nitride and a layer made of silicon oxide. The first interlayer insulating film 16 has a laminated structure of, for example, a layer made of silicon oxide and a layer made of silicon nitride, and the second interlayer insulating film 17 is made of, for example, silicon nitride.

  In the embodiment shown in FIG. 1, a red color filter layer GFR, a green color filter CFG, and a blue color filter CFB are provided at the positions of the region R, the region G, and the region B on the second interlayer insulating film 17, respectively. It has been. The red color filter CFR transmits light in the red wavelength region. The green color filter CFG transmits light in the green wavelength region. The blue color filter CFB transmits light in the blue wavelength region.

  FIG. 2 is a diagram illustrating an example of absorption spectra of the red color filter CFR, the green color filter CFG, and the blue color filter CFB. In FIG. 2, the vertical axis represents the light transmittance with respect to the color filter layer, and the horizontal axis represents the wavelength of light passing through the color filter. In FIG. 2, the absorption spectrum of the red color filter CFR is indicated by 〇, the absorption spectrum of the green color filter CFG is indicated by Δ, and the absorption spectrum of the blue color filter CFB is indicated by □. Each filter layer is made of a material such as glass or plastic. Further, as the color filter layer, CCM (color conversion medium) may be used, or both a material such as glass or plastic and CCM may be used.

  As shown in FIG. 1, a planarizing film 18 is formed on the second interlayer film 17 so as to cover the red color filter layer CFR, the green color filter layer CFG, and the blue color filter layer CFB.

  The planarizing film 18 is formed as follows. For example, an acrylic photosensitive resin is applied by spin coating, and then pre-baked (for example, at 80 ° C. for 10 minutes) in a thermostatic bath or a hot plate. Thereafter, the photosensitive resin on the drain electrode 13d is exposed and developed to form a contact hole, and further post-baked (for example, at 190 ° C. for 15 minutes) to completely cure the resin.

  Next, a transparent conductive film made of indium-tin oxide (ITO) or the like is formed with a thickness of 100 nm on the planarizing film 18 by sputtering or the like. In this example, after forming a transparent conductive film, etching is performed for a predetermined time with 15% hydrochloric acid to form irregularities having a surface roughness Ra of 4 nm or more on the surface of the transparent conductive film. The transparent conductive film can be formed by a known method, for example, a sputtering method, a CVD method, an electron beam evaporation method, etc. Among them, the sputtering method is preferable.

  After etching the transparent conductive film, the surface of the transparent conductive film is washed with isopropyl alcohol, a resist pattern is formed on the transparent conductive film by a photolithography process, and then the hole injection electrode 2 is formed by etching. The hole injection electrode 2 and the drain electrode 13d are electrically connected by a contact hole.

  Next, the pixel isolation film 19 is formed so as to cover the hole injection electrode 2 between the regions R, G, and B using the same material as that used for forming the planarizing film 18.

  Next, as shown in FIG. 1, the organic EL element WL is formed on the regions R, G, and B as follows.

  The organic EL element WL includes a hole injection electrode 2, a hole injection layer 3, a hole transport layer 4, an orange light emitting layer 5a that emits orange light, a blue light emitting layer 5b that emits blue light, an electron transport layer 6, and an electron injection layer 7. , And the electron injection electrode 8. The layers from the hole injection layer 3 to the electron injection layer 7 correspond to the organic laminated film in the present invention.

  A hole injection layer 3 is formed on the entire region so as to cover the hole injection electrode 2 and the pixel isolation film 19. The hole injection layer 3 is made of, for example, fluorocarbon (CFx) having a thickness of 1 nm.

  On the hole injection layer 3, a hole transport layer 4 and an orange light emitting layer 5a are formed in this order. The hole transport layer 4 is formed of NPB so as to have a thickness of 60 nm, for example. The orange light emitting layer 5a has a composition in which a first dopant and a second dopant are doped in a host material, and is formed to have a thickness of 30 nm, for example.

  As the host material of the orange light emitting layer 5a, for example, the same NPB as the material of the hole transport layer 4 is used. As the first dopant of the orange light emitting layer 5a, tBuDPN is used and doped so as to be 20% by weight with respect to the orange light emitting layer 5a.

  As the second dopant of the orange light emitting layer 5a, for example, DBzR is used and doped so as to be 3% by weight with respect to the orange light emitting layer 5a.

  The second dopant of the orange light-emitting layer 5a emits light, and the first dopant has both the highest occupied molecular orbital (HOMO) level and the lowest unoccupied molecular orbital (LUMO) level of the host material and the second dopant. Since it has an intermediate value of the level, it plays a role of assisting light emission of the second dopant by promoting energy transfer from the host material to the second dopant. Therefore, the orange light emitting layer 5a emits orange having a peak wavelength larger than 500 nm and smaller than 650 nm.

  Next, the blue light emitting layer 5b is formed on the orange light emitting layer 5a. The blue light emitting layer 5b has a composition in which a first dopant and a second dopant are doped in a host material, and is formed to have a thickness of, for example, 40 nm.

  For example, TBADN is used as the host material of the orange light emitting layer 5a. As the first dopant of the blue light emitting layer 5b, for example, the same NPB as the material of the hole transport layer 4 is used and doped so as to be 10% by weight with respect to the blue light emitting layer 5b.

  As the second dopant of the blue light emitting layer 5b, for example, TBP is used and doped so as to be 2.5% by weight with respect to the blue light emitting layer 5b.

  The second dopant of the blue light-emitting layer 5b emits light, and the first dopant is made of a hole transporting material. By promoting hole transport, recombination of carriers in the blue light-emitting layer 5b is promoted. It plays the role which assists light emission of the dopant. Therefore, the blue light emitting layer 5b emits blue light having a peak wavelength larger than 400 nm and smaller than 500 nm.

  Next, the electron transport layer 6, the electron injection layer 7, and the electron injection electrode 8 are formed on the blue light emitting layer 5b.

  The electron injection layer 6 is formed to have a thickness of 10 nm, for example, and is formed from Alq3.

  The electron injection layer 7 is formed of lithium fluoride (LiF) so as to have a thickness of 1 nm, for example, and the electron injection electrode 8 is formed of aluminum (Al) so as to have a thickness of 200 nm, for example. The film thickness of the entire organic layer is 140 nm, which is thicker than the height of the unevenness of the transparent conductive film. By making the film thickness of the entire organic layer thicker than the height of the unevenness of the transparent conductive film, it is possible to prevent a short circuit or a dark spot between the electron injection electrode 7 and the hole injection electrode 2.

  NPB is N, N′-di (naphthasen-1-yl) -N, N′-diphenylbenzidine and has the following structure.

  tBuDPN is 5,12-bis (4-tertiary-butylphenyl) naphthacene and has the following structure.

  DBzR is 5,12-bis {4- (6-methylbenzothiazol-2-yl) phenyl} -6,11-diphenylnaphthacene and has the following structure.

  TBADN is 2-tertiary-butyl-9,10-di (2-naphthyl) anthracene and has the following structure.

  TBP is 2,5,8,11-tetra-tertiary-butylperylene and has the following structure.

  Alq3 is tris- (8-quinolinato) aluminum (III) and has the following structure.

  FIG. 13 is a view schematically showing the state of the interface between the layers in the hole injection electrode 2, the organic laminated film 10, and the electron injection electrode 8 formed on the substrate 1. The organic laminated film 10 includes a laminated structure of a hole injection layer 3, a hole transport layer 4, an orange light emitting layer 5 a, a blue light emitting layer 5 b, an electron transport layer 6, and an electron injection layer 7.

  As shown in FIG. 13, the surface of the hole injection electrode 2 is etched as described above to form irregularities. Accordingly, irregularities corresponding to the surface roughness Ra of the hole injection electrode 2 are formed at the interface with the organic laminated film 10 laminated thereon. Further, the unevenness is inherited also at the interface of each layer of the organic laminated film 10, and the unevenness is also formed at the interface with the electron injection electrode 8 formed on the organic laminated film 10. Also, irregularities are formed on the surface of the electron injection electrode 8.

(Examples 1-5)
Etching time for etching the hole injection electrode 2 made of a transparent conductive film is 10 minutes (Example 1), 15 minutes (Example 2), 20 minutes (Example 3), 25 minutes (Example 4). 30 minutes (Example 5), and the organic EL device shown in FIG. 1 was produced as described above. “Time” shown in Table 1 indicates time for etching the transparent conductive film.

(Comparative Example 1)
The time for etching the hole injection electrode 2 made of a transparent conductive film was 5 minutes, and an organic EL device was produced in the same manner as in the above example.

(Example 6)
As a material for forming the hole injection electrode 2, indium-zinc oxide (IZO) is used. The thickness of the hole injection electrode 2 made of IZO is set to 100 nm, and etching is performed using 0.1% hydrochloric acid for 30 minutes to form the hole injection electrode. An organic EL element was produced in the same manner as in each of the above examples except that the surface of 2 was uneven.

(Example 7)
FIG. 12 is a schematic cross-sectional view showing a top emission type organic EL element produced in this example. A structural difference from the bottom emission type organic EL element shown in FIG. 1 is as follows.

  That is, in the top emission type organic EL element shown in FIG. 12, a reflective electrode 2b made of aluminum (Al) is formed, a transparent electrode 2a made of ITO is formed thereon, and on this transparent electrode 2a, A hole injection layer 3, a hole transport layer 4, an orange light emitting layer 5a, a blue light emitting layer 5b, an electron transport layer 6, an electron injection layer 7, and an electron injection electrode 8 are formed.

As the electron injection electrode 8, aluminum (Al) is used, and the film thickness is 10 nm, which is a semi-transmissive electrode. A protective film 9 made of SiN _x or the like is formed on the electron injection electrode 8 for moisture prevention, and an adhesive layer 22 made of a photo-curing resin or a thermosetting resin is formed on the protective film 9 through the adhesive layer 22. A sealing substrate 21a is attached. The color filters CFR, CFG and CFB, and the black matrix BM are formed on the sealing substrate 21.

  FIG. 14 is a schematic diagram showing irregularities at the interface between layers of the element structure in the top emission type organic EL element shown in FIG. As shown in FIG. 14, irregularities are formed on the surface of the transparent electrode 2 a made of a transparent conductive film formed on the reflective electrode 2 b under the same etching conditions as in Example 3. Concavities and convexities corresponding to the surface roughness Ra of the concavities and convexities are formed at the interface between the organic laminated film 10 laminated on the transparent electrode 2a and the transparent electrode 2a. In addition, similar irregularities are formed at the interface of each layer in the organic laminated film 10.

  Similar irregularities are also formed at the interface with the electron injection electrode 8 formed on the organic laminated film 10, and similar irregularities are also formed at the interface with the protective film 9 formed on the electron injection electrode 8. Has been.

  As described above, in this example, a top emission type organic EL element was manufactured.

  FIG. 15 is a schematic view for explaining the structure of another example of the top emission type organic EL element. In the embodiment shown in FIG. 15, the first transparent conductive film 2a is formed on the substrate 1, and the surface of the first transparent conductive film 2a is etched to form irregularities. A reflective electrode 2b is formed on the first transparent conductive film 2a having the irregularities, and a transparent electrode 2a made of the second transparent conductive film is formed on the reflective electrode 2b. On the second transparent conductive film 2a, the organic laminated film 10, the electron injection electrode 8, and the protective film 9 are formed in the same manner as in Example 7 to obtain a top emission type organic EL element.

(Comparative Example 2)
In Examples 1 to 5, organic EL elements were produced in the same manner as in the above examples except that the hole injection electrode 2 was not etched.

(Comparative Example 3)
In Example 7, a top emission type organic EL element was produced in the same manner as in Example 7 except that the transparent electrode 2a was not subjected to the etching treatment.

[Evaluation of organic EL elements]
When producing the organic EL elements of Examples 1 to 7 and Comparative Examples 1 to 3, the surface roughness of the surface of the transparent conductive film subjected to the etching treatment was measured. The surface roughness was measured using an atomic force microscope AFM (Nanoscope IIIa manufactured by Beiko Japan). Moreover, the inclination angle of the surface irregularities was measured simultaneously. Table 1 shows the measured surface roughness Ra and the inclination angle.

  Further, the light extraction efficiency of light emitted from each organic EL element and the angle dependency of luminance and chromaticity were measured. For the measurement, BM5A manufactured by Topcon Corporation was used, and the change in luminance (change in light extraction efficiency) and change in chromaticity at the front (0 °) and 60 ° were measured. The measurement results are shown in Table 1.

  As is clear from the comparison between Comparative Example 1 and Examples 1 to 5, the surface roughness Ra of the surface of the transparent conductive film is set to 4 nm or more, whereby the light extraction efficiency is improved and the viewing angle dependency is improved. It turns out that it reduces. As described above, the surface roughness Ra of the surface of the transparent conductive film corresponds to the unevenness at the interface between the light extraction side electrode and the organic multilayer film in each organic EL element. It can be understood that the light extraction efficiency is improved and the viewing angle dependency is reduced by making the unevenness of the interface of the surface to be unevenness corresponding to a surface roughness Ra of 4 nm or more.

  Further, as apparent from Comparative Example 1 and Examples 1 to 5, it can be seen that the surface roughness Ra can be adjusted by changing the etching processing time.

  Further, as is clear from the comparison between Example 5 and Example 6, it is found that when IZO is used as the transparent conductive film, the surface roughness Ra and the inclination angle are increased.

  3-10 is a figure which shows the surface state of the transparent conductive film after the etching process in Comparative Examples 1 and 2 and Examples 1-6, and is the figure obtained by AFM observation. 3 is Comparative Example 1, FIG. 4 is Example 1, FIG. 5 is Example 2, FIG. 6 is Example 3, FIG. 7 is Example 4, FIG. 8 is Example 5, FIG. 10 shows the surface state of the transparent conductive film of Comparative Example 2.

  FIG. 11 is a diagram showing the surface state of the reflective electrode in Example 3. As is clear from the comparison between FIG. 11 and FIG. 6, it can be seen that the same unevenness as that of the surface of the transparent conductive film is formed on the surface of the reflective electrode.

The typical sectional view showing the element structure of the bottom emission type organic EL element of one example according to the present invention. The figure which shows the relationship between the wavelength of each color filter used in the Example according to this invention, and the transmittance | permeability. The figure which shows the uneven | corrugated state of the surface of the transparent conductive film after the etching in the comparative example 1. FIG. The figure which shows the uneven | corrugated state of the surface of the transparent conductive film after the etching in Example 1. FIG. The figure which shows the uneven | corrugated state of the surface of the transparent conductive film after the etching in Example 2. FIG. The figure which shows the uneven | corrugated state of the surface of the transparent conductive film after the etching in Example 3. FIG. The figure which shows the uneven | corrugated state of the surface of the transparent conductive film after the etching in Example 4. FIG. The figure which shows the uneven | corrugated state of the surface of the transparent conductive film after the etching in Example 5. FIG. The figure which shows the uneven | corrugated state of the surface of the transparent conductive film after the etching in Example 6. FIG. The figure which shows the uneven | corrugated state of the surface of the transparent conductive film after the etching in the comparative example 2. FIG. FIG. 6 is a diagram showing a concavo-convex state on the surface of a reflective electrode in Example 3. Typical sectional drawing which shows the element structure of the top emission type organic EL element of the other Example according to this invention. The figure which shows the uneven | corrugated state of the interface between each layer in the bottom emission type organic EL element in the Example according to this invention. The figure which shows the uneven | corrugated state of the interface between each layer in the top emission type organic EL element in the Example according to this invention. The figure which shows the uneven | corrugated state of the interface between each layer in the top emission type organic EL element in the Example according to this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Hole injection electrode 2a ... Transparent conductive film (transparent electrode)
2b ... reflective electrode 3 ... hole injection layer 4 ... hole transport layer 5a ... orange light emitting layer 5b ... blue light emitting layer 6 ... electron transport layer 7 ... electron injection layer 8 ... electron injection electrode

Claims (8)

An organic electroluminescence device comprising a light extraction side electrode, a reflection electrode, and an organic laminated film including a light emitting layer disposed between the light extraction side electrode and the reflection electrode,
The organic electroluminescence device is characterized in that irregularities corresponding to a surface roughness Ra of 4 nm or more are formed at an interface between the light extraction side electrode and the organic laminated film. A bottom emission type organic electroluminescence element,
The light extraction side electrode made of a transparent conductive film is provided on a substrate, the organic laminated film is provided on the light extraction side electrode, and the reflective electrode is provided on the organic laminated film. The organic electroluminescent element according to claim 1, wherein   Concavities and convexities corresponding to the concavities and convexities of the interface between the light extraction side electrode and the organic multilayer film are inherited at the interface in the organic multilayer film and the interface between the organic multilayer film and the reflective electrode. The organic electroluminescent element according to claim 2. A top emission type organic electroluminescence device,
The reflective electrode is provided on a substrate, a transparent conductive film is provided on the reflective electrode, the organic laminated film is provided on the transparent conductive film, and the organic laminated film The light extraction side electrode is provided on the top,
Concavities and convexities corresponding to a surface roughness Ra of 4 nm or more are formed at the interface between the transparent conductive film and the organic multilayer film. The organic electroluminescence device according to claim 1, wherein unevenness corresponding to Ra 4 nm or more is formed. A top emission type organic electroluminescence device,
A first transparent conductive film is provided on the substrate, the reflective electrode is provided on the first transparent conductive film, and a second transparent conductive film is provided on the reflective electrode. The organic laminated film is provided on the second transparent conductive film, the light extraction side electrode is provided on the organic laminated film,
Concavities and convexities corresponding to a surface roughness Ra of 4 nm or more are formed at the interface between the first transparent conductive film and the reflective electrode. The organic electroluminescence device according to claim 1, wherein irregularities corresponding to a roughness Ra of 4 nm or more are formed. A method for producing the organic electroluminescent element according to claim 2, comprising:
Forming the light extraction side electrode made of a transparent conductive film on a substrate;
Etching the surface of the light extraction side electrode to form irregularities with a surface roughness Ra of 4 nm or more;
A step of sequentially forming the organic laminated film and the reflective electrode on the light extraction side electrode. A method for producing the organic electroluminescent device according to claim 4, comprising:
Forming the reflective electrode on a substrate;
Forming the transparent conductive film on the reflective electrode;
Etching the surface of the transparent conductive film to form irregularities having a surface roughness Ra of 4 nm or more;
And a step of sequentially forming the organic laminated film and the light extraction side electrode on the transparent conductive film. A method for producing the organic electroluminescent device according to claim 5, comprising:
Forming the first transparent conductive film on a substrate;
Etching the surface of the first transparent conductive film to form irregularities having a surface roughness Ra of 4 nm or more;
Forming the reflective electrode, the second transparent conductive film, the organic laminated film, and the light extraction side electrode in order on the first transparent conductive film. Device manufacturing method.