JP2010010235A - Organic light-emitting display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic light-emitting display device of long life, wherein a light-emitting layer is easily formed by a wet method. <P>SOLUTION: The organic light-emitting display device includes a light-emitting layer and an upper electrode and lower electrode sandwiching the light-emitting layer. One of the upper electrode and lower electrode is a transparent electrode which allows the light emitted from the light-emitting layer to pass through while the other is a reflection electrode that reflects the light emitted from the light-emitting layer, with a water content-capturing layer arranged between the upper electrode and the lower electrode. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an organic light emitting display device.

  In recent years, organic light emitting display devices have attracted attention as next-generation flat display devices. This organic light emitting display device has excellent characteristics such as self light emission, wide viewing angle, and high-speed response characteristics.

  Usually, the structure of an organic light emitting device is configured by forming a transparent electrode such as ITO, an organic EL layer composed of a hole transport layer, a light emitting layer, an electron transport layer, and the like, and a low work function reflective electrode on a glass substrate. The emitted light passes through the electrode and is extracted from the back surface of the glass substrate.

In such an organic light emitting display device, it has become possible to realize high efficiency and long life by forming each organic layer by a vacuum deposition method. For example, R. Meerheim et al. Disclosed in Non-Patent Document 1 that a red organic light-emitting device having a luminance half time of 1.5 million hours or more can be produced by a vacuum deposition method with an initial luminance of 500 cd / m ² . Yes. On the other hand, as a method for manufacturing an organic light emitting display device without using a vacuum evaporation method, there is a method of forming an organic layer by a spin coating method or an ink jet method. The lifetime and efficiency of an organic light emitting display device formed by such a wet method is smaller than that of an organic light emitting device formed by a vacuum deposition method. The lifetime of a red organic light emitting device formed by a spin coating method using a polymer material is disclosed in Non-Patent Document 2 as about 100,000 hours at an initial 500 cd / m ² , but compared with Non-Patent Document 1. , About 1/10, life is shortened.

Recently, studies have been made to form a low-molecular material by a coating method, which is disclosed in Non-Patent Document 3, but the lifetime of the red organic light-emitting element is about 25000 hours or more at an initial 500 cd / m ² , Compared with an element formed by vapor deposition using a low molecular material as disclosed in Patent Document 1, the lifetime is short. Thus, the element which formed the light emitting layer with the wet method has a short lifetime.

JP 2004-185967 A Appl. Phys. Lett., 89, 061111 (2006) IDW’06, p.441 (2006) IDW’07, p241 (2007)

  An object of the present invention is to provide an organic light emitting display device which can easily form a light emitting layer by a wet method and has a long lifetime.

  That is, the organic light emitting display device of the present invention is an organic light emitting display device comprising a light emitting layer, and an upper electrode and a lower electrode sandwiching the light emitting layer, wherein either one of the upper electrode and the lower electrode. Is a transparent electrode that transmits light emitted from the light-emitting layer, and the other is a reflective electrode that reflects light emitted from the light-emitting layer, and a moisture trap layer is disposed between the upper electrode and the lower electrode. It is characterized by having.

  According to the said structure, deterioration of the light emitting layer by a water | moisture content can be suppressed, and a long-life organic light emitting display apparatus can be formed simply.

  Hereinafter, embodiments of the organic light emitting display device of the present invention will be described with reference to the drawings.

  FIG. 1 is a configuration example of a cross-sectional view of a red pixel portion of a bottom emission type organic light emitting display device that extracts emitted light from a lower electrode side. In FIG. 1, on a glass substrate 1, in order, a first interlayer insulating film 2, a second interlayer insulating film 3, a power line 4, an image signal line 5, a third interlayer insulating film 6, a transparent electrode 7 (lower electrode) ), A bank 8, an organic EL layer 9, a blocking layer 10, a moisture capturing layer 11, an electron transporting layer 12, and an upper electrode 13 (reflection electrode). FIG. 2 is a diagram showing a cross-sectional structure of the pixel central portion of the organic EL layer 9. The organic EL layer 9 includes a hole injection layer 14, a hole transport layer 15, and a light emitting layer 16 in order from the bottom in FIG.

  The moisture capturing layer 11 is disposed between the transparent electrode 7 (lower electrode) and the reflective electrode 13 (upper electrode).

  The lower electrode 7 is a transparent electrode having transparency of light emitted from the light emitting layer 16. ITO is used for the lower electrode 7, and pattern formation can be performed by photolithography. The anode material used for the lower electrode 7 may be any material having transparency and a high work function, such as a conductive oxide such as IZO or a metal having a large work function such as thin Ag other than ITO. .

Bank 8 separates adjacent pixels. An acrylic resist material is used for the bank 8. Pattern formation was performed using photolithography. After insolubilizing the bank 8 by heat treatment, the surface of the bank 8 is made water-repellent by CF ₄ plasma treatment. The material of the bank 8 is not limited to acrylic resist, and various polymer materials such as polyimide resin, phenol resin, novolac resin, and epoxy resin can be used.

  The hole injection layer 14 is a layer that injects holes from the lower electrode 7. PEDOT (poly (3,4-ethylene dioxythiophene): PSS (polystyrene sulfonate) is used for the hole injection layer 14. The material used for the hole injection layer 14 is not limited to PEDOT: PSS. Further, materials such as polypyrrole-based materials and triphenylamine-based polymers can be used, and they can be combined with low-molecular materials, and phthalocyanine compounds and starburst amine-based compounds can also be used.

  The hole transport layer 15 is a layer that transports holes. For the hole transport layer 15, an allylamine polymer is used. In addition to these, various polymers such as polyfluorene, polyparaphenylene, polyarylene, and polycarbazole can be used.

  The light emitting layer 16 is a layer in which injected holes and electrons are recombined to emit light at a wavelength specific to the material. The light emitting layer 16 contains a host material and a light emitting dopant. Here, CBP (4,4'-di (N-carbazolyl) biphenyl) represented by the following h-1 was used as the host material, and an Ir complex represented by the following d-1 was used as the luminescent dopant. . The weight ratio of the host material to the luminescent dopant was 10: 1. A coating solution in which the host material and the light emitting dopant were dissolved was prepared, and the light emitting layer 16 was formed from the coating solution by a wet method. As the wet method, for example, an inkjet method, a printing method, a spray method, or the like can be applied. In this example, an inkjet method was used to form a film using a solution having a solid content concentration of 0.5 wt%. When forming by the inkjet method, the viscosity of the solution (ink) is desirably 1 to 20 mPa · s (room temperature). There is no restriction | limiting in particular of solid content concentration of a solution, What is necessary is just solid content concentration which can form a desired film thickness. As the solution, a solvent in which a polar solvent such as aromatic or alcohol was mixed was used. These solvents may be used alone.

それぞれの材料は、上記の材料に限定されるわけではない。例えば、ホスト材料としては、４，４′，４″−トリ（Ｎ−カルバゾリル）トリフェニルアミン（ＴＣＴＡ）やＮ，Ｎ′−ジカルバゾリル−３，５−ベンゼン（ｍＣＰ）などのカルバゾール誘導体や、アルミニウム（III）ビス（２−メチル−８−キノリナト）４−フェニルフェノレート）（Ｂａｌｑ）などのキノリノール錯体やイリジウム錯体も用いることができる。また、これらの材料を２種類以上混合することもできる。また、上記の材料以外に、ポリカーボネートなどのバインダとなる高分子材料を混合して用いることができる。また、トリフェニルアミン誘導体のような正孔輸送材料やオキサジアゾール誘導体やトリアゾール誘導体などの電子輸送性材料も混合して用いることができる。発光ドーパントとしては、上記のＩｒ錯体だけではなく、その他のＩｒ錯体，Ｐｔ錯体，Ｏｓ錯体などの燐光発光材料を用いることができる。また、それ以外にもジスチリルアリレン誘導体やクマリン誘導体，キナクリドン誘導体などの蛍光発光材料も用いることができる。

Each material is not limited to the above materials. For example, as a host material, carbazole derivatives such as 4,4 ′, 4 ″ -tri (N-carbazolyl) triphenylamine (TCTA) and N, N′-dicarbazolyl-3,5-benzene (mCP), aluminum (III) Quinolinol complexes and iridium complexes such as bis (2-methyl-8-quinolinato) 4-phenylphenolate) (Balq) can also be used, and two or more of these materials can be mixed. In addition to the above materials, a polymer material serving as a binder such as polycarbonate can be mixed and used, and a hole transport material such as a triphenylamine derivative, an electron such as an oxadiazole derivative or a triazole derivative, and the like. A transporting material can also be used as a mixture, and the luminescent dopant is the above Ir complex. Instead, other phosphorescent materials such as Ir complexes, Pt complexes and Os complexes can be used, and other fluorescent materials such as distyrylarylene derivatives, coumarin derivatives and quinacridone derivatives can also be used. it can.

  The blocking layer 10 blocks excitons formed in the light emitting layer 16 and holes injected into the light emitting layer 16 from being injected into the electron transport layer 12. For the blocking layer 10, aluminum (III) bis (2-methyl-8-quinolinato) 4-phenylphenolate) (Balq) was used. The material of the blocking layer 10 is not limited to this material, and other quinolinol complexes, oxazole derivatives, triazole complexes, polycyclic condensed hydrocarbons, and the like can be used.

  The moisture capturing layer 11 is a feature of the present invention and captures moisture in the thin film of the device. Barium oxide was used for the moisture trap layer 11. The material of the moisture trap layer 11 is not limited to this material, but is an oxide such as lithium oxide, calcium oxide, strontium oxide, aluminum oxide, and phosphorus pentoxide, or a metal such as Li, Ba, Ca, and Cs, Alternatively, a metal carbonate such as calcium carbonate, a Schiff base such as [w1], or the like can be used. You may use these individually by 1 type or in mixture of 2 or more types.

電子輸送層１２は、電子を輸送する層である。電子輸送層１２には、トリス（８−キノリノラト）アルミニウム（Ａｌｑ₃）を用いた。電子輸送層１２の材料は、上記に限られるわけではなく、例えば、その他のキノリノール誘導体やオキサジアゾール誘導体，トリアゾール誘導体，フラーレン誘導体，フェナントロリン誘導体，キノリン誘導体などを用いることができる。

The electron transport layer 12 is a layer that transports electrons. For the electron transport layer 12, tris (8-quinolinolato) aluminum (Alq ₃ ) was used. The material of the electron transport layer 12 is not limited to the above, and other quinolinol derivatives, oxadiazole derivatives, triazole derivatives, fullerene derivatives, phenanthroline derivatives, quinoline derivatives, and the like can be used, for example.

  The upper electrode 13 is a reflective electrode having reflectivity of light emitted from the light emitting layer 16. For the upper electrode 13, a laminate of LiF and Al was used. In addition to LiF, Cs compounds, Ba compounds, Ca compounds, etc., electron transport materials, alkali metals such as Li, Cs, alkaline earth metals, and electron-donating organic materials are co-evaporated in addition to LiF. Materials can be used.

  FIG. 3 is a cross-sectional view of a red light emitting pixel portion created as Comparative Example 1. FIG. 4 shows a cross-sectional view of the organic EL layer 29. This Comparative Example 1 is different from FIG. 1 in that it does not have the moisture capturing layer 11 (see FIG. 1).

  The luminance half-life of the red light emitting pixel portion of this example was 1.2 times that of the luminance half-life of Comparative Example 1 described above. As described above, according to the organic light emitting display device of this embodiment, the moisture in the light emitting layer 16 is reduced, deterioration due to moisture is suppressed, and the life can be extended.

  In this embodiment, the blocking layer 10 and the electron transport layer 12 are common to each pixel. The present invention is not particularly limited to the structure, and the blocking layer 10 and the electron transport layer 12 may have a structure using different materials for each pixel.

  5 and 6 are a cross-sectional view of a red light emitting pixel portion and a cross-sectional view of an organic EL layer 49 in Example 2. The difference from FIG. 1 is that the moisture trapping layer 50 is between the light emitting layer 56 and the blocking layer 51, and the light emitting dopant concentration contained in the light emitting layer 56 is low in the vicinity of the blocking layer 51, and in the vicinity of the hole transport layer 55. It is a high so-called inclined structure.

  The luminance half life of the red light emitting pixel portion of this example was 1.2 times that of Comparative Example 1 described above.

  7 and 8 are a cross-sectional view of the red light emitting pixel portion and a cross-sectional view of the organic EL layer 69 in Example 3. The difference from FIG. 5 is that the light emitting host material of the light emitting layer 76 is Balq instead of CBP. CBP has the same hole mobility and electron mobility, and is a material that can carry both carriers. In contrast, Balq is a so-called electron transporting material in which the electron mobility is higher than the hole mobility. Therefore, recombination of electrons and holes occurs in the vicinity of the hole transport layer 75 of the light emitting layer 76.

  The luminance half life of the red light emitting pixel portion of this example was 1.5 times that of Comparative Example 1 described above.

  The difference between the present embodiment and the first embodiment is that the light emitting layer 16 (see FIG. 1) contains polycarbonate. The luminance half life of the red light emitting part of this example was 1.3 times that of Comparative Example 1 described above.

  FIG. 9 is a cross-sectional view of the red light emitting unit of the fifth embodiment. FIG. 10 is a cross-sectional view of the organic EL layer 91 of FIG. Example 5 is the same as Example 1 except for the following points. That is, the moisture trap layer 90 is disposed between the hole injection layer 89 and the hole transport layer 94. The luminance half life of the red light emitting part of Example 5 was 1.2 times that of Comparative Example 1.

  FIG. 11 is a cross-sectional view of the red light emitting pixel portion of the sixth embodiment. Example 6 is the same as Example 1 except for the following points. That is, instead of the bank 8 (see FIG. 1), a liquid-repellent thin film was provided between the pixels (not shown in FIG. 11). A fluorine compound was used for the thin film having liquid repellency. Solubility / insolubility was controlled by light irradiation, and a liquid repellent part was formed between pixels. Thereby, the light emitting layer 110 can be formed only in the pixel portion.

  Comparative Example 2 is the same as Example 6 except for the following points. That is, in Comparative Example 2, there is no moisture trap layer 11 (see FIG. 1). The luminance half life of the red light emitting part of Example 6 was 1.2 times that of Comparative Example 2.

  FIG. 12 is a cross-sectional view of the red light emitting pixel portion of the seventh embodiment. FIG. 13 is a cross-sectional view of the organic EL layer 129 of FIG. Example 7 is the same as Example 1 except for the following points. That is, the lower electrode (reflection electrode) is used instead of the lower electrode (transparent electrode). An Al / ITO laminated film was used for the lower electrode (reflection electrode). This material is not particularly limited to this, and Ag or the like can be used instead of Al. Further, a transparent electrode such as IZO or ZnO can be used instead of ITO. Further, instead of the laminated structure of the metal and the transparent conductive film as described above, Cr, MoW, or the like can be used.

  Comparative Example 3 is the same as Example 7 except for the following points. That is, the structure has no moisture trap layer 131 (see FIG. 12). The luminance half life of the red light emitting part of Example 7 was 1.2 times that of the power efficiency of Comparative Example 3.

  In Example 7, all the organic light emitting display devices had a so-called top cathode type top emission structure. However, the structure of the present invention is not limited thereto, and can be applied to a so-called top anode type structure.

  In the above embodiment, only the red light emitting part is described. However, by appropriately selecting the light emitting dopant, the hole transporting material, and the electron transporting material, the light emitting part of other colors can be used. . For example, the following [d2] and [d3] light emitting dopants can be used to cope with green or blue. Of course, the following materials are not limited, and the performance can be further improved by using a material having a structure that is not point-symmetric.

  According to the present invention, a long-life organic light-emitting display device can be easily produced, and is suitable for display devices such as televisions and various information terminals.

1 is a cross-sectional view of a red pixel portion of an embodiment of an organic light emitting display device according to the present invention. It is sectional drawing of the organic electroluminescent layer of FIG. FIG. 6 is a cross-sectional view of a red pixel portion of another embodiment of the organic light emitting display device according to the present invention. It is sectional drawing of the organic electroluminescent layer of FIG. FIG. 6 is a cross-sectional view of a red pixel portion of another embodiment of the organic light emitting display device according to the present invention. It is sectional drawing of the organic electroluminescent layer of FIG. FIG. 6 is a cross-sectional view of a red pixel portion of another embodiment of the organic light emitting display device according to the present invention. It is sectional drawing of the organic electroluminescent layer of FIG. FIG. 6 is a cross-sectional view of a red pixel portion of another embodiment of the organic light emitting display device according to the present invention. It is sectional drawing of the organic electroluminescent layer of FIG. FIG. 6 is a cross-sectional view of a red pixel portion of another embodiment of the organic light emitting display device according to the present invention. FIG. 6 is a cross-sectional view of a red pixel portion of another embodiment of the organic light emitting display device according to the present invention. It is sectional drawing of the organic electroluminescent layer of FIG.

Explanation of symbols

1, 21, 41, 61, 81, 101, 121 Glass substrate 2, 22, 42, 62, 82, 102, 122 First interlayer insulating film 3, 23, 43, 63, 83, 103, 123 Second interlayer Insulating film 4, 24, 44, 64, 84, 104, 124 Power line 5, 25, 45, 65, 85, 105, 125 Image signal line 6, 26, 46, 66, 86, 106, 126 Third interlayer insulation Membrane 7, 27, 47, 67, 87, 107 Transparent electrode (lower electrode)
8, 28, 48, 68, 88, 128 Bank 9, 29, 49, 69, 91, 129 Organic EL layer 10, 30, 51, 71, 111, 130 Blocking layer 11, 50, 70, 90, 112, 131 Moisture trap layers 12, 32, 52, 72, 92, 113, 132 Electron transport layers 13, 33, 53, 73, 93, 114 Upper electrodes 14, 34, 54, 74, 89, 108, 134 Hole injection layer 15 , 35, 55, 75, 94, 109, 135 Hole transport layer 16, 36, 56, 76, 95, 110, 136 Light emitting layer 127 Reflective electrode (lower electrode)
133 Transparent electrode (upper electrode)

Claims (12)

A light emitting layer;
An upper electrode and a lower electrode sandwiching the light emitting layer;
An organic light emitting display device comprising:
One of the upper electrode and the lower electrode is a transparent electrode that transmits light emitted from the light emitting layer, and the other is a reflective electrode that reflects light emitted from the light emitting layer, and the upper electrode and the lower electrode An organic light-emitting display device, wherein a moisture capturing layer is disposed between electrodes.   The organic light emitting display device according to claim 1, wherein the moisture trapping layer is disposed between the light emitting layer and the upper electrode.   Further, the blocking layer and the electron transport layer are disposed between the upper electrode and the lower electrode, and the moisture capturing layer is disposed between the blocking layer and the electron transport layer. The organic light emitting display device according to claim 2.   The said moisture capture layer is adjacent to the said light emitting layer, The dopant density | concentration of the said light emitting layer adjacent to the said moisture capture layer is small compared with the other side of Claim 2 characterized by the above-mentioned. Organic light-emitting display device.   The organic light emitting display device according to claim 2, wherein the moisture capturing layer is adjacent to the light emitting layer, and a light emitting region of the light emitting layer is separated from the moisture capturing layer.   Furthermore, a blocking layer is disposed between the upper electrode and the lower electrode, the moisture trapping layer is disposed between the light emitting layer and the blocking layer, and the light emitting layer includes an electron transporting material. The organic light-emitting display device according to claim 2.   3. The organic light emitting display device according to claim 2, further comprising a bank having a water repellent treated surface disposed between the upper electrode and the lower electrode.   The organic light emitting display device according to claim 2, wherein a light emitting dopant of the light emitting layer has an asymmetric structure.   The organic light emitting display device according to claim 2, wherein at least one of the materials constituting the light emitting layer has an asymmetric structure.   The organic light emitting display device according to claim 2, wherein the light emitting layer includes a polymer material.   3. The organic light emitting display device according to claim 2, wherein a thin film having liquid repellency is disposed between the pixels.   The organic light emitting display device according to claim 1, wherein the moisture capturing layer includes a metal and / or a metal oxide.

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