JP4703107B2 - Manufacturing method of organic EL element - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention includes an organic EL (Electroluminescence) element, particularly a light scattering structure. Manufacturing method of organic EL element About.
[0002]
[Prior art]
An EL element utilizing a phenomenon in which light is emitted when an electric field is applied to a substance or electrons are injected has attracted attention as a self-luminous electronic display. Both organic compounds and inorganic compounds have been studied and put into practical use as light emitting materials. In particular, an organic EL element using an organic compound in a light emitting layer can emit light at a low applied voltage, and development of a device having high brightness and high quality is being actively conducted.
[0003]
6A to 6E are schematic cross-sectional views showing conventional organic EL elements.
[0004]
Reference is made to FIG. For example, a transparent electrode 63 that is an anode formed of a transparent conductive material such as ITO (Indium Tin Oxide), for example, on a light-transmitting substrate 62 formed of a flat glass substrate, an organic that emits light when current is passed In the case of the light emitting layer 64, for example, a non-translucent cathode, the counter electrode 65 which is a cathode formed of aluminum is laminated in this order. The light emitted from the organic light emitting layer 64 is extracted from the light extraction surface 61 on the light transmissive substrate 62 side.
[0005]
The organic light emitting layer 64 may have a single layer structure including only the light emitting layer, but may be composed of a plurality of layers as described below. Note that the organic light emitting layer 64 in the case of a single layer structure is often formed using a polymer material. The light emitting layer is formed of, for example, an aluminum complex, and emits light by recombination of electrons supplied from the cathode and holes supplied from the anode. In the case of a multi-layer structure, the hole transport layer and the electron transport layer improve the transport properties of holes and electrons supplied from, for example, a transparent electrode and a counter electrode, respectively. The hole injection layer and the electron injection layer have a function of increasing carrier injection efficiency from the electrode.
[0006]
6B to 6E are schematic cross-sectional views showing the configuration of the organic light emitting layer 64.
[0007]
Reference is made to FIG. When the organic light emitting layer 64 has a two-layer structure, the organic light emitting layer 64 includes, for example, a hole transport layer 64b formed on the transparent electrode 63 and a light emission / electron transport layer 64a formed thereon. The light emitting / electron transporting layer 64a is a layer formed of a light emitting material having a function of improving the transportability of electrons supplied from the counter electrode 65, for example.
[0008]
Reference is made to FIG. When the organic light emitting layer 64 has a three-layer structure, the organic light emitting layer 64 is formed by laminating, for example, a hole transport layer 64b, a light emitting layer 64d, and an electron transport layer 64c in this order on the transparent electrode 63.
[0009]
Reference is made to FIG. When the organic light emitting layer 64 has a four-layer structure, the organic light emitting layer 64 includes, for example, a hole injection layer 64f, a hole transport layer 64b, a light emitting layer 64d, and an electron injection layer 64e formed in this order on the transparent electrode 63. Being done.
[0010]
Reference is made to FIG. When the organic light emitting layer 64 has a five-layer structure, the organic light emitting layer 64 includes, for example, a hole injection layer 64f, a hole transport layer 64b, a light emission layer 64d, an electron transport layer 64c, and an electron injection layer 64e formed on the transparent electrode 63. Are stacked in this order. In the case of this structure, use of an organic layer doped with an alkali metal as the electron injection layer 64e is effective in reducing the voltage.
[0011]
Generally, an organic EL element is configured by combining materials having different refractive indexes. For example, when the light emitting layer 64d is an organic phosphor layer containing a fluorescent dye, the refractive index thereof is 1.6 to 1.8, and the refractive index of the transparent electrode 63 formed of a transparent conductive material such as ITO is 1.8 to 1.8. 2.2, When the light-transmitting substrate 62 is made of glass, its refractive index is about 1.5. Note that the refractive index of air is 1.0.
[0012]
When light emitted from the organic light emitting layer 64 propagates inside the organic EL element and travels into the air, reflection or refraction occurs at the interface having a different refractive index. As a result, the rate at which the light emitted from the organic light emitting layer 64 of the organic EL element is extracted into the air is about 20 to 30%. In the conventional organic EL element configuration shown in FIGS. 6A to 6E, the light that can be extracted outside of the light emitted from the organic light emitting layer is calculated to be about 20%. (For example, see Non-Patent Document 1 or 2.)
For the purpose of providing a structure in which the specular electrode (counter electrode) constituting the organic EL element is not visually recognized as a mirror surface when the organic EL element is not emitting light, for example, the inner surface (on the same side as the organic light emitting layer) in contact with the substrate There is also a proposal of a structure in which a lenticular lens sheet or a prism lens sheet is provided on the outer surface (opposite side of the organic light emitting layer). There is also a proposal for a structure that relaxes the total reflection condition at the interface between the substrate and air. It has also been reported that the organic EL element having such a structure improves the light extraction efficiency (luminance) to the outside. However, the improvement in luminance is about 1.6 times. (For example, see Patent Document 1.)
[0013]
[Non-Patent Document 1]
MRS Bull. , 22, 39-45 (1997)
[Non-Patent Document 2]
2000 MRS Fall Meeting, JJ5, 27 (2000)
[Patent Document 1]
Japanese Patent No. 2931111
[0014]
[Problems to be solved by the invention]
The object of the present invention is to improve the light extraction efficiency to the outside. Manufacturing method of organic EL element Is to provide.
[0018]
According to one aspect of the present invention, A translucent substrate and a size of 30 nm to 500 nm formed on the substrate; In range A light-scattering layer made of a resin having pores, a translucent first electrode formed on the light-scattering layer, and an organic light-emitting layer formed on the first electrode and capable of emitting light And a second electrode formed on the organic light emitting layer, wherein the substrate is irradiated with ultraviolet rays immediately after an ultraviolet curable composition containing a volatile solvent is applied onto the substrate. Hardened by The size of 30 nm to 500 nm In range There is provided a method for producing an organic EL element, comprising a step of forming a light scattering layer made of a resin having pores.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
The inventors of the present application have simplified a sample of how the loss of transmittance until the light emitted from the light emitting layer is emitted from the substrate is changed by changing the layer structure or the like (here) Then, it is called an organic light emitting element). Since the light emitting layer can emit light by ultraviolet excitation or the like, the electrode is omitted.
[0021]
1A to 1E are schematic cross-sectional views showing a plurality of organic light-emitting elements having different structures, and FIG. 1F is an organic light-emitting device shown in FIGS. 1A to 1E. It is a table | surface which shows the brightness | luminance of the light taken out outside the element about each of an element. In all the organic light emitting devices shown in FIGS. 1A to 1E, a non-alkali glass plate (Corning 1737) was used for the light transmissive substrate 62. In addition, the organic light emitting devices shown in FIGS. 1A, 1B, 1D, and 1E are not formed in the conventional organic EL devices shown in FIGS. 6A to 6E. An additional layer 67 is formed.
[0022]
FIG. 1A is a cross-sectional view schematically showing a first sample 11 of an organic light emitting device. The light transmitting substrate 62 (non-alkali glass plate) was washed and degreased to form an additional layer 67 on one main surface.
[0023]
The additional layer 67 comprises 16 parts by weight of UV-crosslinked acrylate monomer, 11 parts by weight of UV-crosslinked acrylate oligomer, 10 parts by weight of acrylic resin, 3 parts by weight of amino resin, 27 parts by weight of toluene, 18 parts by weight of butyl acetate, and 8 parts by weight of methyl isobutyl ketone. After the UV curable composition containing 5 parts by weight of methanol and 2 parts by weight of the polymerization initiator was coated on the light-transmitting substrate 62, the UV light of the high pressure mercury lamp was immediately 3.5 J / cm. ² It was formed by irradiating (at 365 nm) and drying at room temperature.
[0024]
The cured UV curable composition was entirely white in appearance (white resin layer) and had light scattering properties.
[0025]
The SEM image of the ultraviolet curable composition (white resin layer) was shown to FIG. 7 (A) and (B). The pore shape was random, and the pore size was several tens to 500 nm. The resin composition appears to be composed of fine particles of about several tens to 300 nm and secondary particles formed by aggregation of these fine particles. Furthermore, when the pore diameter distribution of the ultraviolet curable composition formed on the glass substrate with a mercury porosimeter was measured, it had a peak at 52 nm.
[0026]
Next, on the surface of the additional layer 67, tris (8-quinolinolato) aluminum (Alq) which is an organic fluorescent material is used. ₃ ) Was vacuum-deposited to form the organic light emitting layer 64, and the first sample 11 was obtained.
[0027]
FIG. 1B is a cross-sectional view schematically showing a second sample 12 of the organic light emitting device. One side of the light-transmitting substrate 62 (non-alkali glass plate) was polished with a No. 800 carborundum and processed into a frost shape to form an additional layer 67. Next, on the frosted side (on the additional layer 67), Alq ₃ The organic light emitting layer 64 was formed by vacuum deposition, and the second sample 12 was obtained.
[0028]
FIG. 1C is a cross-sectional view schematically showing a third sample 13 of the organic light emitting device. The light transmissive substrate 62 (non-alkali glass plate) is washed and degreased, and Alq is formed on one main surface. ₃ The organic light emitting layer 64 was formed by vacuum deposition, and a third sample 13 was obtained.
[0029]
FIG. 1D is a cross-sectional view schematically showing a fourth sample 14 of the organic light emitting device. The light transmitting substrate 62 (non-alkali glass plate) was washed and degreased to form an additional layer 67 on one main surface. The formation method is the same as the formation method of the additional layer 67 of the first sample 11 shown in FIG.
[0030]
Next, on the main surface of the light transmissive substrate 62 where the additional layer 67 is not formed, Alq ₃ The organic light emitting layer 64 was formed by vacuum deposition, and a fourth sample 14 was obtained. In the first sample 11, the additional layer 67 is formed on the main surface of the light-transmitting substrate 62 on the same side as the organic light-emitting layer 64. In the fourth sample 14, the additional layer 67 is light-transmissive. On the main surface of the substrate 62, it is formed on the side opposite to the organic light emitting layer 64.
[0031]
FIG. 1E is a cross-sectional view schematically illustrating a fifth sample 15 of the organic light emitting device. One main surface of the light-transmitting substrate 62 (non-alkali glass plate) was polished with a No. 800 carborundum and processed into a frost shape to form an additional layer 67. This is cleaned and degreased, and Alq is formed on the main surface (the main surface on which the additional layer 67 is not formed) on which the light transmitting substrate 62 is not frosted. ₃ The organic light emitting layer 64 was formed by vacuum deposition, and a fifth sample 15 was obtained.
[0032]
In the second sample 12, the additional layer 67 is formed on the main surface of the light transmissive substrate 62 on the same side as the organic light emitting layer 64, but in the fifth sample 15, the additional layer 67 is light transmissive. On the main surface of the substrate 62, it is formed on the side opposite to the organic light emitting layer 64.
[0033]
FIG. 1 (F) shows that when five samples of the first sample 11 to the fifth sample 15 of the organic light emitting device are irradiated with 365 nm ultraviolet light from the organic light emitting layer 64 side, the light is emitted from the opposite surface. It is a table | surface which shows the front brightness | luminance of emitted light. Front brightness is in units of “cd / m” ² " The front luminance means the luminance of light emitted in the direction perpendicular to the main surface of the light transmissive substrate 62.
[0034]
It can be seen that the front luminance of the other samples having the additional layer 67 is higher than the front luminance of the third sample 13 in which the additional layer 67 is not formed. By forming the additional layer 67 on the main surface of the light transmissive substrate 62 on the same side as the organic light emitting layer 64 or on the opposite side thereof, the light emission luminance of the organic light emitting element can be improved.
[0035]
Further, from the comparison between the first sample 11 and the fourth sample 14 and the comparison between the second sample and the fifth sample 15, the additional layer 67 is replaced with the organic light emitting layer 64 of the light transmissive substrate 62. By forming in contact with the main surface on the same side (additional layer 67 is formed not between light-transmitting substrate 62 and air, but between light-transmitting substrate 62 and organic light-emitting layer 64), organic light emission It can be seen that the light emission luminance of the element can be further improved.
[0036]
Furthermore, from the comparison between the first sample 11 and the second sample 12, it is better to form the white resin layer as the additional layer 67 than when the optically transparent substrate 62 is frosted to form the additional layer 67. It can be seen that the light emission luminance of the organic light emitting device can be further improved.
[0037]
Even when the white resin layer is not formed as a single continuous film, but is formed discontinuously on a large number of fine parts (for example, when it is formed in a fine houndstooth pattern), the light emission luminance is reduced. Could be improved.
[0038]
Even if the additional layer 67 is formed of a resin or glass having a porous structure having a pore diameter of 30 nm to 10 μm, the emission luminance can be improved.
[0039]
An actual organic EL element has a pair of electrodes that sandwich an organic light emitting layer. Experiments were conducted on how the transmitted light changes by inserting an electrode between the organic light emitting layer and the substrate. The counter electrode remains omitted.
[0040]
2A and 2B are schematic cross-sectional views showing two organic light-emitting elements having different structures, and FIG. 2C is an organic light-emitting device shown in FIGS. 2A and 2B. It is a table | surface which shows the brightness | luminance of the light taken out outside the element about each of an element. FIG. 2D is a table comparing the luminance of light extracted outside the element for the third sample 13 and the seventh sample 17. In the organic light emitting device shown in FIGS. 2A and 2B, a non-alkali glass plate (Corning 1737) was used for the light transmissive substrate 62. Further, in the organic light emitting device shown in FIG. 2 (A), an additional layer 67 that is not formed in the conventional organic EL device shown in FIGS. 6 (A) to (E) is formed.
[0041]
FIG. 2A is a cross-sectional view schematically showing a sixth sample 16 of the organic light emitting device. After cleaning and degreasing the light transmissive substrate 62 (non-alkali glass plate), an additional layer 67 was formed on one main surface. The formation method is the same as the formation method of the additional layer 67 in the first sample 11 shown in FIG.
[0042]
Next, SiO 2 having a thickness of 520 mm is formed on the additional layer 67 by RF sputtering. ₂ A transparent electrode 63 made of a thin film and an ITO thin film having a thickness of 1360 mm was formed. Further, after the transparent electrode 63 is heated and dried, the Alq is formed on the transparent electrode 63. ₃ The organic light emitting layer 64 was formed by vacuum deposition, and a sixth sample 16 was obtained. Heat drying is SiO ₂ After the thin film and the ITO thin film are formed, the permeable substrate 62 is once taken out into the atmosphere, so that degassing (desorption of the ITO surface adsorption gas and the additional layer 67 (white resin layer)) is performed.
[0043]
FIG. 2B is a cross-sectional view schematically showing a seventh sample 17 of the organic light emitting device. After cleaning and degreasing the light transmissive substrate 62 (non-alkali glass plate), the transparent electrode 63 was formed on one main surface, and the organic light emitting layer 64 was further formed on the transparent electrode 63. The configuration, thickness, material, and formation method of the transparent electrode 63 and the organic light emitting layer 64 are the same as in the case of the sixth sample 16 shown in FIG.
[0044]
FIG. 2C shows that when two samples of the sixth sample 16 and the seventh sample 17 of the organic light emitting device are irradiated with 365 nm ultraviolet light from the organic light emitting layer 64 side, the light is emitted from the opposite surface. It is a table | surface which shows the front brightness | luminance of emitted light. Front brightness is in units of “cd / m” ² "
[0045]
From the comparison between the sixth sample 16 and the seventh sample 17, it is possible to remarkably improve the luminance of the organic light emitting device by providing the additional layer 67 between the light transmissive substrate 62 and the transparent electrode 63. Recognize.
[0046]
FIG. 2 (D) shows that the device fabrication conditions for the third sample 13 and the seventh sample 17 are unified, and when both samples are irradiated with 365 nm ultraviolet light from the organic light emitting layer 64 side, It is a table | surface which shows the front luminance of the light discharge | released from a surface. Front brightness is in units of “cd / m” ² " UV light has a front luminance of 100 cd / m for the third sample 13. ² Irradiation was performed under such conditions.
[0047]
The front luminance of the seventh sample 17 is about 20% larger than that of the third sample 13.
[0048]
The present inventors interpreted the results shown in FIGS. 2C and 2D as follows.
[0049]
In the third sample 13, due to total reflection, part of the light emitted from the organic light emitting layer 64 is confined in the organic light emitting layer 64, and another part is confined in the light transmissive substrate 62. It is thought to be smaller. The seventh sample 17 having the transparent electrode 63 between the organic light emitting layer 64 and the light transmissive substrate 62 has a brightness about 20% higher than that of the third sample 13 because the light is slightly scattered by the transparent electrode 63. This is probably because light trapped in the organic light emitting layer 64 or the light transmissive substrate 62 is reduced. However, since the ITO forming the transparent electrode 63 has a high refractive index of 1.9, light from the organic light emitting layer 64 (for example, refractive index 1.7) easily enters the transparent electrode 63, while light is transmitted through the transparent electrode 63. Because of the total reflection, light hardly enters the conductive substrate 62 (in the case of being formed of glass, the refractive index is 1.5). That is, it seems that light newly confined in the transparent electrode 63 is generated.
[0050]
The brightness of the sixth sample 16 is 2.6 times the brightness of the seventh sample 17 because the additional layer 67 formed between the light transmissive substrate 62 and the transparent electrode 63 is light transmissive substrate. It is considered that the light totally reflected at the interface between the additional layer 67 and the adjacent layer is reduced by scattering the light incident from the 62 side and the transparent electrode 63 side.
[0051]
In the first sample 11 in which the additional layer 67 is formed between the organic light emitting layer 64 and the light transmissive substrate 62, the additional layer 67 is incident from the organic light emitting layer 64 side and the light transmissive substrate 62 side. It is considered that the light that is totally reflected at the interface between the additional layer 67 and the layer adjacent to the additional layer 67 is reduced and the luminance is improved by scattering the light that is transmitted. The reason why the first sample 11 has a larger luminance than the sixth sample 16 is that the difference in refractive index between the organic light emitting layer 64 and the additional layer 67 is smaller than that between the transparent electrode 63 and the additional layer 67. In the first sample 11, the light incident on the additional layer 67 from the organic light emitting layer 64 side and scattered is more than the light incident on the additional layer 67 from the transparent electrode 63 side and scattered in the sixth sample 16. Because of that.
[0052]
As described above, the reason why the luminance of the sample in which the additional layer 67 is formed is high is that the light incident on the additional layer 67 has a structure that scatters in a plurality of directions. Then, as the additional layer 67 having the same function, for example, the following can be considered.
[0053]
The additional layer 67 may be, for example, a thin film composition in which a medium that reflects light is mixed or a reflective surface is provided. For example, a structure in which a crack, a through hole, a hole, or the like is provided in the layer, or a structure in which regions having different compositions are formed in the layer by phase separation or the like can be considered.
[0054]
Further, the additional layer 67 may be a thin-film composition in which a material having a refractive index different from that of the transparent material is dispersed in a material transparent to the light emitted from the organic light emitting layer 64, for example. Transparent materials include glass, transparent resin, silicon dioxide (SiO ₂ ), Metal oxides, and the like can be used. The transparent material may be formed from one type of material, or may be formed from a plurality of types of materials. The dispersion in the transparent material may be, for example, bubbles, SiO ₂ Particles, resin particles, metal powder, metal oxide particles. Each dispersion preferably has a diameter of 10 nm to several tens of μm, and more preferably 50 nm to several μm. The size of the dispersion may be uniform or non-uniform. By dispersing the dispersion irregularly, light can be scattered in a plurality of directions. The density of the dispersion may vary depending on the location. You may disperse | distribute to the whole additional layer 67, and may disperse | distribute to a one part area | region. Furthermore, the dispersion mode may change in the thickness direction of the additional layer 67 as long as it has light scattering properties.
[0055]
Further, the additional layer 67 may be a layer formed including a surface having irregular irregularities, for example. The surface including the unevenness may be formed on the surface of the additional layer 67 or may be formed inside. Even if it is formed on both the surface and the inside, it is effective. The size of the unevenness varies depending on the wavelength of light to be scattered, but in the case of visible light, it is preferable to use an unevenness having a diameter of 400 nm to 100 μm. The uneven surface is, for example, SiO ₂ , PMMA, polytetrafluoroethylene (PTFE) or the like is formed by forming a concavo-convex composition on the light transmissive substrate 62 by spraying, printing, vapor deposition, sputtering, sol-gel, precipitation, or the like. Further, the surface of the light transmissive substrate 62 may be processed so as to have irregular irregularities, and the portion including the processed portion may be regarded as the additional layer 67.
[0056]
Further, the additional layer 67 may be a layer formed by including a portion obtained by processing the light-transmitting substrate 62 into a frost shape by physical polishing or chemical etching. Frost processing is performed to a roughness greater than that capable of scattering light from the organic light emitting layer 64.
[0057]
The additional layer 67 is made of a material having a refractive index different from that of the light transmissive substrate 62 or the transparent electrode 63, for example, a material having a refractive index that is an intermediate value between the refractive index of the light transmissive substrate 62 and the refractive index of the transparent electrode 63. It may be a formed layer. For example, the additional layer 67 is made of SiO. ₂ It is formed of a transparent material in which particles, resin particles, metal powder, and metal oxide particles are dispersed. The particle size is preferably 10 nm to several hundred nm. For example, the additional layer 67 is fixed to the light transmissive substrate 62 by a resin adhesive, spraying, vapor deposition, sputtering, dip, spin coating or the like. It may be dispersed and fixed in an organic or inorganic binder or solvent. Further, the additional layer 67 is laminated by, for example, an electrophoresis method or a substrate pulling method. The particle size of the material forming the additional layer 67 may be uniform or non-uniform. By distributing the particles irregularly, light can be scattered in a plurality of directions. The thickness to be fixed or laminated may be any thickness that allows the light from the organic light emitting layer 64 to be scattered.
[0058]
By forming the additional layer 67 as described above, among the light generated in the organic light emitting layer 64, the light confined inside the organic light emitting element can be reduced, and much light can be extracted outside the organic light emitting element. It is considered possible.
[0059]
In the sixth sample 16, the additional layer 67 is formed between the light transmissive substrate 62 and the transparent electrode 63. However, the transparent electrode 63 is formed on the light transmissive substrate 62, and the additional layer 67, Even if the organic light emitting layer 64 is formed in order (even if the additional layer 67 is formed between the transparent electrode 63 and the organic light emitting layer 64), the organic light emitting with improved luminance can be used as long as the function as the organic light emitting element is not impaired. An element could be realized. For example, the organic light emitting layer 64 includes at least one of a light emitting layer 64d capable of emitting light and a hole injection layer 64f or a hole transport layer 64b, and the hole injection layer 64f or the hole transport layer 64b included in the organic light emitting layer 64. An organic light emitting device having a structure in which at least one of the light scatters light in a plurality of directions (for example, the structure described above as the additional layer 67) can be considered.
[0060]
FIG. 3 is a graph showing the relationship between the emission angle of the emitted light and the brightness enhancement effect due to the insertion of the additional layer, for four samples of organic light emitting devices each having an additional layer with a different haze ratio. The horizontal axis of the graph indicates the emission angle of the emitted light in the unit of “degree (°)”. In addition, the vertical axis represents the change in luminance of light emitted from the organic light emitting device having an additional layer with respect to the luminance of light emitted from the organic light emitting device having no additional layer at each emission angle as a luminance improvement effect. Indicated by “double”. The haze rate (%) is defined by {(diffuse transmittance) / (total light transmittance)} × 100, and is a value defined by JIS K7136.
[0061]
The graphs A to D in the figure each have the same structure as the sixth sample 16 shown in FIG. 2A, and the haze ratio of the additional layer 67 is A: 20%, B: 39%, and C: The relationship between the emission angle of the emitted light and the brightness enhancement effect is shown for an organic light emitting device having 61% and D: 82%. When the sample of the above four organic light emitting devices is irradiated with 365 nm ultraviolet light from the organic light emitting layer 64 side, the luminance of the light emitted from the opposite surface is measured for each emission direction (emission angle). The graph of FIG. 3 was obtained.
[0062]
It can be seen that the luminance of all four organic light emitting devices having the additional layer 67 having haze ratios of 20%, 39%, 61%, and 82% is remarkably improved. When the additional layer 67 having a haze ratio of 20 to 82% is formed on the organic light emitting device, the luminance can be remarkably improved. When the organic light emitting layer 64 is an organic light emitting device including at least one of the hole injection layer 64f and the hole transport layer 64b having a structure that scatters light in a plurality of directions, the hole injection layer 64f or the hole transport layer 64b included. If the total haze ratio is 20 to 82%, the luminance can be remarkably improved. Note that the haze ratio can be controlled by the thickness of the additional layer 67. It can also be controlled by the resin composition and pore density.
[0063]
FIG. 8 is a graph showing the relationship between the haze ratio and the layer thickness of the additional layer 67 (ultraviolet curable composition (white resin layer)). The horizontal axis represents the haze ratio in “%”, and the vertical axis represents the layer thickness in the unit “μm”.
[0064]
When the haze ratio is expressed on a linear scale and the layer thickness is expressed on a logarithmic scale, there is a linear relationship between the two. From this graph, it can be seen that the haze ratio of the additional layer 67 can be controlled by the layer thickness.
[0065]
4 (A) and 4 (B) are schematic views showing organic EL elements according to examples.
[0066]
Reference is made to FIG. In the organic EL element shown in FIG. 4A, a light scattering layer 66 is formed between the transparent electrode 63 and the light transmissive substrate 62 in the conventional organic EL element shown in FIG. Other configurations are the same as those of the conventional example shown in FIG. The light scattering layer 66 in FIG. 4A corresponds to the additional layer 67 in the sample of the organic light emitting element described with reference to FIG.
[0067]
The organic light emitting layer 64 includes at least a light emitting layer (light emitting portion) that emits light by recombination of holes and electrons, and as described above, an electron transport layer, an electron injection layer, a hole transport layer, a hole injection layer, and the like. May be included.
[0068]
The material for forming the light-emitting layer (light-emitting portion) is a polymer such as polymethyl methacrylate (PMMA) or polycarbonate (PC), a molecular dispersion polymer in which a small amount of an organic light-emitting material such as coumarin is dispersed, or a PC skeleton. Electron-injecting oxadiazole derivatives dispersed in polymers introduced with distyrylbenzene derivatives, conjugated polymers such as polyphenylene vinyl derivatives and polyalkylthiophene derivatives, and hole-transporting polyvinyl carbazole Etc. are used.
[0069]
As a material for forming the hole transport layer, conductive polymer oligomers such as triazole derivatives, oxadiazole derivatives, and imidazole derivatives are used.
[0070]
As a material for forming the electron injection layer, an electron transfer compound such as a nitro-substituted fluorenone derivative, an anthraquinodimethane derivative, or a diphenylquinone derivative is used.
[0071]
In addition, as a material for forming the organic light emitting layer 64 using only an organic light emitting material, fluorescent whitening agents such as benzothiazole and benzimidazole, metal chelated oxinoid compounds, styrylbenzene compounds and the like are used.
[0072]
The above is a polymer-based organic EL element material, but an organic EL element can also be fabricated using a low-molecular material. Since the low molecular organic EL material can be vacuum-deposited, there is an advantage that the manufacturing process can be simplified.
[0073]
Aromatic amine hole injection materials and hole transport materials such as copper phthalocyanine, diamine and triphenylamine, electron transport materials such as aluminum quinolinol complex, oxadiazole and triazole, coumarin, dicyanomethylenepyran (DCM) ) Fluorescent dye materials typified by derivatives, such as Ir (ppy) ₃ A phosphorescent light-emitting material centered on an iridium (Ir) complex such as is used as the low-molecular EL material.
[0074]
For the light-transmitting substrate 62, a light-transmitting (transparent) resin such as polyethylene terephthalate (PET), PMMA, PC, polyethersulfone (PES), and triacetyl cellulose (TAC) is used in addition to glass. Can do. Further, the range of light to be transmitted is not limited to the visible light wavelength region (380 to 780 nm), but light in the near ultraviolet / ultraviolet region, light in the near infrared / infrared region, depending on the purpose of use of the organic EL element. The light-transmitting substrate 62 includes those that transmit the light.
[0075]
For the transparent electrode 63, in addition to ITO, a conductive inorganic material such as zinc oxide or tin oxide, or a conductive polymer material such as polyaniline (PANi) or poly3,4-ethylenedioxythiophene (PEDOT) is used. It is done.
[0076]
The light scattering layer 67 has a structure that scatters incident light in a plurality of directions. The structure shown as a specific example of the additional layer 67 will be considered as a specific example of the light scattering layer 67.
[0077]
In an organic EL device having a structure in which light generated in the organic light emitting layer is emitted to the outside from the light transmissive substrate side, a difference in refractive index is obtained by providing a light scattering layer between the transparent electrode and the light transmissive substrate. It is considered that the interface reflection caused by the light can be reduced, and the light extraction efficiency to the outside of the element and the luminance can be improved.
[0078]
Reference is made to FIG. The organic EL element shown in FIG. 4B has a hole transport layer instead of the hole transport layer 64b when the organic light emitting layer 64 of FIG. 6A has a three-layer structure as shown in FIG. A light scattering hole transport layer 64g provided with a light scattering structure in 64b is formed. As the light scattering structure, a structure similar to the structure shown as a specific example of the additional layer 67 can be employed. However, as a structure corresponding to the additional layer 67 formed of a material having a refractive index different from that of the light transmissive substrate 62 or the transparent electrode 63, at least one of the hole injection layer 64f and the hole transport layer 64b is used as the transparent electrode 63 or the light emitting layer 64d. For example, a structure formed of a material having an intermediate refractive index can be considered.
[0079]
By providing a light scattering structure in the hole transport layer, an organic EL device with improved light extraction efficiency and brightness to the outside of the device can be produced. In addition to the structure shown in FIG. 4B, the organic light emitting layer can emit light, and the hole transport layer having the light scattering structure or the hole injection layer having the light scattering structure. If at least one of them is present, the light extraction efficiency and the luminance to the outside of the element can be improved.
[0080]
By employing the structure shown in FIG. 4A or FIG. 4B, an organic EL element with improved light extraction efficiency to the outside of the element can be manufactured easily and inexpensively.
[0081]
FIG. 5 is a schematic cross-sectional view of an organic EL element having a plurality of light emitting regions and a structure for selectively emitting light from these light emitting regions. The organic light emitting layers 64x, y, z between the pair of transparent electrodes 63x, y, z and the counter electrodes 65x, y, z are regions that can selectively emit light. Not only the organic EL element having one light emitting region but also the organic EL device having a plurality of light emitting regions, the light extraction layer 66 is formed to extract light from the organic light emitting layer 64 to the outside. In addition, the luminance can be improved.
[0082]
In the embodiment, the organic EL element having a structure in which light is extracted from the transparent substrate side is handled. However, the present invention can be applied to an organic EL element having a structure in which light is extracted from the counter electrode side. That is, light can be extracted from a plane parallel to the substrate.
[0083]
The organic EL element by an Example can be used for the organic EL apparatus provided with organic EL elements, such as a display panel and a display, as a light emission source.
[0084]
As mentioned above, although this invention was demonstrated along the Example, this invention is not limited to these. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.
[0085]
【The invention's effect】
As described above, according to the present invention, an organic EL element with improved light extraction efficiency can be provided.
[Brief description of the drawings]
FIGS. 1A to 1E are schematic cross-sectional views showing a plurality of organic light-emitting elements having different structures, and FIG. 1F is a cross-sectional view of the organic light-emitting elements shown in FIGS. It is a table | surface which shows the brightness | luminance of the light taken out outside the element about each.
FIGS. 2A and 2B are schematic cross-sectional views showing two organic light-emitting elements having different structures, and FIG. 2C is a diagram of the organic light-emitting elements shown in FIGS. It is a table | surface which shows the brightness | luminance of the light taken out outside the element about each, (D) is an element about the organic light emitting element shown in FIG.1 (C) and the organic light emitting element shown in FIG.2 (B). It is the table | surface which compared the brightness | luminance of the light taken out outside.
FIG. 3 is a graph showing the relationship between the emission angle of emitted light and the brightness enhancement effect due to the insertion of an additional layer for four samples of organic light emitting devices each having an additional layer with different haze ratios.
4A and 4B are schematic views showing an organic EL device according to an example. FIG.
FIG. 5 is a schematic cross-sectional view of an organic EL element having a plurality of light emitting regions and a structure for selectively emitting light from those light emitting regions.
6A to 6E are schematic cross-sectional views showing a conventional organic EL element.
7A and 7B are SEM images of an ultraviolet curable composition (white resin layer).
FIG. 8 is a graph showing the relationship between haze ratio and layer thickness of an additional layer (ultraviolet curable composition (white resin layer)).
[Explanation of symbols]
11 First sample
12 Second sample
13 Third sample
14 Fourth sample
15 Fifth sample
16 Sixth sample
61 Light extraction surface
62 Light transmissive substrate
63, 63x, y, z Transparent electrode
64, 64x, y, z Organic light emitting layer
64a Light emitting / electron transport layer
64b hole transport layer
64c electron transport layer
64d light emitting layer
64e electron injection layer
64f hole injection layer
64g Light scattering hole transport layer
65, 65x, y, z Counter electrode
66 Light scattering layer
67 Additional layers

Claims (1)

A translucent substrate;
A light scattering layer made of a resin having pores in the size range of 30 nm to 500 nm formed on the substrate;
A translucent first electrode formed on the light scattering layer;
An organic light emitting layer formed on the first electrode and capable of emitting light;
A method for producing an organic EL device having a second electrode formed on the organic light emitting layer,
On the substrate, an ultraviolet curable composition containing a volatile solvent is applied and then cured by irradiation with ultraviolet rays to form a light scattering layer made of a resin having pores in the size range of 30 nm to 500 nm. The manufacturing method of the organic EL element characterized by having the process to do.

Images