JPWO2005094133A1 - Arylamine compound and organic electroluminescence device - Google Patents

Abstract

The present invention provides an arylamine compound having a molecular weight of 1500 to 6000 represented by the following general formula (1) and an organic electroluminescence device containing the compound. According to the present invention, an arylamine compound having excellent hole injection / transport properties and capable of forming a stable thin film is provided. By using the compound, luminous efficiency and durability of a conventional organic EL device are provided. Can be significantly improved.

Description

  The present invention relates to a compound and an element suitable for an organic electroluminescence (EL) element which is a self-luminous element suitable for various display devices, and more specifically, an arylamine compound having a molecular weight of 1500 to 6000, and the compound. The present invention relates to the organic EL element used.

やその誘導体（例えば、特許文献３参照）が提案されているが、これらは塗布によって安定な薄膜を形成させることができない。
［特許文献３］ 特開平４−３０８６８８号公報
また、有機ＥＬ素子の耐久性を高めるためには薄膜安定性の良い化合物を用いると良いとされている。薄膜安定性はアモルファス性の高い化合物ほど高く、アモルファス性の指標としてガラス転移点（Ｔｇ）が用いられている（例えば、非特許文献３参照）。
［非特許文献３］ Ｍ＆ＢＥ研究会Ｖｏｌ．１１ Ｎｏ．１ ３２〜４１頁 発行年：２０００（社）応用物理学会発行
ガラス転移点（Ｔｇ）は高いほど良いとされているが、ＭＴＤＡＴＡのガラス転移点は７６℃で、アモルファス性が高いとは言えない。そのため、有機ＥＬ素子の耐熱性などの耐久性において、また、正孔注入・輸送の特性に起因する発光効率においても、満足な素子特性が得られていなかった。Since organic EL elements are self-luminous elements, they have been actively researched because they are brighter and more visible than liquid crystal elements and can be clearly displayed.
In 1987, Eastman Kodak's C.I. W. Tang et al. Have developed an organic EL element using an organic material by developing a two-layer type laminated structure element. They laminate a phosphor that transports electrons and an organic substance that transports holes, and inject both charges into the phosphor layer to emit light, so that they can emit 1000 cd / m ² or more at a voltage of 10 V or less. High brightness can be obtained (see, for example, Patent Document 1 and Patent Document 2).
[Patent Document 1] Japanese Patent Application Laid-Open No. 8-48656 [Patent Document 2] Japanese Patent No. 3194657 An organic EL element is an element using an evaporation type low molecular weight material due to a difference in element manufacturing process and material characteristics. And coating type elements mainly using polymer materials.
The vapor deposition type element requires a vacuum vapor deposition apparatus for film formation, but the coating type element can easily form a film by applying the coating liquid to the substrate and then removing the solvent in the coating liquid. Therefore, the manufacturing process becomes simple and can be manufactured at low cost. Since it can be easily applied by an ink jet method, a spray coating method, or a printing method, expensive equipment is not required for production.
A general material used for manufacturing a coating-type element is a polymer material such as poly (1,4-phenylene vinylene) (hereinafter abbreviated as PPV) (for example, see Non-Patent Document 1). ).
[Non-Patent Document 1] Applied Physics Letters 71-1, page 34 (1997)
Further, an organic EL element in which the role of the two layers is further subdivided and a hole injection layer, a hole transport layer, and an electron transport layer are provided separately from the light emitting layer has been studied. Poly (ethylenedioxythiophene) / poly (styrene sulfonate) (hereinafter abbreviated as PEDOT / PSS) is used as a hole injection or transport material for producing a hole injection layer or a hole transport layer by coating. Widely used (see Non-Patent Document 2, for example).
[Non-Patent Document 2] Optical Materials 9 (1998) 125
However, since the PEDOT / PSS coating solution is an aqueous gel dispersion hydrated by PSS in which the molecular chain of PEDOT has an ionic interaction, it is an acidic aqueous solution. For this reason, there are difficulties in use, such as application of an application liquid such as an inkjet discharge head and corrosion of a printing apparatus.
Further, it has been pointed out that PSS in the coating film adversely affects the anode and that water used in the coating solution remains in the element, leading to deterioration during driving. Furthermore, it is said that the thiophene ring of PEDOT is reduced by the inflow of electrons. Because of these disadvantages, PEDOT / PSS cannot be said to be a sufficient hole injecting / transporting material, and satisfactory device characteristics have not been obtained particularly in terms of durability.
On the other hand, as a hole injection / transport material in a vapor deposition type element, copper phthalocyanine or MTDATA represented by the following formula:

And derivatives thereof (see, for example, Patent Document 3) have been proposed, but these cannot form a stable thin film by coating.
[Patent Document 3] Japanese Patent Application Laid-Open No. 4-308688 In addition, in order to increase the durability of the organic EL element, it is preferable to use a compound having good thin film stability. The thin film stability is higher as the amorphous compound is higher, and the glass transition point (Tg) is used as an amorphous index (see, for example, Non-Patent Document 3).
[Non-Patent Document 3] M & BE Study Group Vol. 11 No. 1 Pages 32 to 41 Publication year: 2000 (published by the Japan Society of Applied Physics) The higher the glass transition point (Tg), the better, but the MTDATA glass transition point is 76 ° C, and it cannot be said that the amorphous nature is high. . For this reason, satisfactory element characteristics have not been obtained in terms of durability such as heat resistance of the organic EL element and also in light emission efficiency resulting from the characteristics of hole injection / transport.

An object of the present invention is to provide a homogeneous compound having excellent hole injection / transport properties and excellent amorphous properties as a highly efficient and highly durable organic EL device material.
Another object of the present invention is to provide a highly efficient and highly durable organic EL device using the above compound.
The physical properties of the compound suitable for the present invention are as follows: (1) high amorphous property and suitable for film formation by coating; (2) excellent hole injection ability; and (3) hole transport ability. (4) It has a glass transition point of 150 ° C. or higher and the thin film state is stable. In addition, the physical characteristics of the element suitable for the present invention include (1) film formation by coating, (2) high luminous efficiency, (3) high maximum emission luminance, and (4) lamination by coating. It can be mentioned that an element can be manufactured.

（式中、Ｘは単結合、ＣＨあるいはＣＨ_２、または、ＮあるいはＮＨを表し、Ａｒ_１、Ａｒ_２、Ａｒ_３はフェニル基、ビフェニル基またはターフェニル基を表し、Ｒ_１、Ｒ_２、Ｒ_３、Ｒ_４、Ｒ_５、Ｒ_６はそれぞれ独立にアリール基を表し、このアリール基はさらにトリフェニルアミン部分構造を形成するようにしてジアリールアミノ基で置換されていてもよく、さらに末端のアリール基は繰り返してトリフェニルアミン様の部分構造を形成するようにしてジアリールアミノ構造含有基で置換されていてもよい。ｎは０または１を表す。）
本発明の一般式（１）で表される分子量１５００以上６０００以下のアリールアミン化合物の中で好ましいのは、分子内に窒素原子を９個または１０個有しているもの、特に好ましくは１０個有しているものである。また、一般式（１）で表される分子量１５００以上６０００以下のアリールアミン化合物の中で好ましいのは、分子内にトリフェニルアミン様の部分構造を７〜９個有しているものである。
一般式（１）中における基Ｒ_１〜Ｒ_６の具体例としては、置換もしくは無置換のフェニル基、置換もしくは無置換のビフェニル基、置換もしくは無置換のナフチル基、置換もしくは無置換のターフェニル基があげられる。
本発明の一般式（１）で表される分子量１５００以上６０００以下のアリールアミン化合物は、優れた正孔注入・輸送特性を有するばかりでなく、塗布によって安定な薄膜を容易に形成することができる。この結果、高効率、高耐久性の有機ＥＬ素子を実現できることが明らかになった。
本発明の有機ＥＬ素子は、優れた正孔注入・輸送特性を有し、かつ安定な薄膜を形成する分子量１５００以上６０００以下のアリールアミン化合物を用いたため、高効率、高耐久性を実現することができる。Therefore, in order to achieve the above object, the present inventors designed and chemically synthesized an arylamine compound having a molecular weight of 1500 to 6000 and a novel compound thereof, and various organic EL compounds using the compound. As a result of prototyping an element and intensively evaluating the characteristics of the element, the present invention was completed.
That is, the object of the present invention is an organic electroluminescence device having an arylamine compound having a molecular weight of 1500 to 6000 represented by the general formula (1), and a pair of electrodes and at least one organic layer sandwiched therebetween. This was achieved by providing an organic electroluminescent device containing the compound as a constituent material of at least one organic layer.

(In the formula, X represents a single bond, CH or CH ₂ , or N or NH, Ar ₁ , Ar ₂ , and Ar ₃ represent a phenyl group, a biphenyl group, or a terphenyl group, and R ₁ , R ₂ , R 3 ₃ , R ₄ , R ₅ and R ₆ each independently represents an aryl group, and this aryl group may be further substituted with a diarylamino group so as to form a triphenylamine partial structure. The group may be substituted with a diarylamino structure-containing group so as to form a triphenylamine-like partial structure repeatedly, and n represents 0 or 1.)
Among the arylamine compounds having a molecular weight of 1500 or more and 6000 or less represented by the general formula (1) of the present invention, those having 9 or 10 nitrogen atoms in the molecule, particularly preferably 10 It is what you have. Further, among the arylamine compounds having a molecular weight of 1500 to 6000 represented by the general formula (1), those having 7 to 9 triphenylamine-like partial structures in the molecule are preferable.
Specific examples of the groups R _{1 to} R ₆ in the general formula (1) include a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted naphthyl group, a substituted or unsubstituted terphenyl. Group.
The arylamine compound having a molecular weight of 1500 or more and 6000 or less represented by the general formula (1) of the present invention not only has excellent hole injection / transport properties, but also can easily form a stable thin film by coating. . As a result, it has become clear that a highly efficient and highly durable organic EL element can be realized.
Since the organic EL device of the present invention uses an arylamine compound having a molecular weight of 1500 to 6000 that has excellent hole injection / transport properties and forms a stable thin film, it can achieve high efficiency and high durability. Can do.

  The present invention is an arylamine compound having a molecular weight of 1500 or more and 6000 or less, which is useful as a material for a hole injection layer or a hole transport layer of an organic EL device, and is an organic EL device produced using the compound. . According to the present invention, the light emission efficiency and durability of a conventional coating type organic EL element can be remarkably improved.

FIG. 1 is a chart of TOF-MS.
FIG. 2 is an enlarged chart of TOF-MS.
FIG. 3 is a diagram showing an EL element configuration of Example 8.
FIG. 4 is a diagram showing an EL element configuration of Example 9.
FIG. 5 is a diagram showing an EL element configuration of Example 10.
FIG. 6 is a diagram showing an EL element configuration of Example 11.
FIG. 7 is a graph comparing the voltage / current density characteristics of Example 8 and Comparative Examples 1 and 2.
FIG. 8 is a graph comparing the voltage / luminance characteristics of Example 8 and Comparative Examples 1 and 2.
FIG. 9 is a graph comparing the current density / luminance characteristics of Example 8 and Comparative Examples 1 and 2.
FIG. 10 is a graph comparing the current density / current efficiency of Example 8 and Comparative Examples 1 and 2.
In addition, the code | symbol in a figure represents the following, respectively.
1: Glass substrate 2: Transparent anode 3: Hole injection layer 4: Hole transport layer 5: Light emitting layer / electron transport layer 6: Hole blocking layer 7: Cathode

尚、「ジアリールアミノ構造含有基」としては、上記例示化合物に示されているように、４−（ジアリールアミノ）フェニル基や、４−（ジアリールアミノ）フェニル基を構成する一部のフェニル基あるいはフェニレン基に置換基を有するものが挙げられる。また、本明細書において「トリフェニルアミン様の部分構造」とは、無置換のトリフェニルアミン構造の他に、置換基を有するトリフェニルアミン構造および上記式（４）や（６）の化合物が有する末端構造を包含するものである。
本発明の化合物の精製はカラムクロマトグラフによる精製、溶媒による再結晶や晶析法などによって行った。カラム精製などにより単一分子種にまで精製することができた。化合物の構造は元素分析などによって同定した。本発明の化合物が有する特徴の一つは、分子量が大きいにもかかわらず、高分子材料のような多種の分子種の混合物ではなく、単一の分子種で構成されていることである。
本発明者らは、単一分子種であることを実証する手段として、化合物をイオン化して電位差空間をドリフトさせて検出する、飛行時間型質量分析装置（以後、ＴＯＦ−ＭＳと略称する）を用いた。ＴＯＦ−ＭＳを用いた分析結果は、本発明に用いた化合物の均質性を実証している。高純度の単一分子種であるために、有機ＥＬ素子の耐久劣化の要因である不純物によるキャリアトラップが少なく、有機ＥＬ素子を構成する有機層として好適である。
化合物の物性値として、ＤＳＣ測定（Ｔｇ）と融点の測定を行った。融点は蒸着性の指標となり、ガラス転移点（Ｔｇ）は薄膜状態の安定性の指標となる。融点とガラス転移点は、粉体を用いて、マックサイエンス製の示差走査熱量測定装置を用いて測定した。
また仕事関数は、ＩＴＯ基板の上に１００ｎｍの薄膜を作成して、理研計器製の大気中光電子分光装置ＡＣ２を用いて測定した。仕事関数は正孔注入能力の指標となるものである。
本発明の化合物は、塗布液を作製し、塗布によって薄膜を成膜して有機ＥＬ素子を作製することができる。塗布液を作製するために用いる溶媒にはシクロヘキサンやＴＨＦ、トリクロロエタンやｏ−ジクロロベンゼンなどの溶媒が適している。塗付液には発光材料や電子輸送材料などの機能性の化合物を混合することができる。
塗布液を用いた成膜方法として、スピンコート法、キャスティング法、マイクログラビア法、グラビアコート法、バーコート法、ロールコート法、ワイアーバーコート法、ディップコート法、スプレーコート法、スクリーン印刷法、フレキソ印刷法、オフセット印刷法、インクジェット印刷法などの塗布方法を用いることができる。
塗膜の厚さは、有機ＥＬ素子の駆動電圧と耐久性が最適となるように選択できる。少なくてもピンホールが発生しないような厚さが必要であり、あまり厚いと有機ＥＬ素子の駆動電圧が高くなって好ましくない。従って、塗膜の膜厚は、例えば１ｎｍから１μｍであり、好ましくは１０〜２００ｎｍである。
本発明の有機ＥＬ素子の構造としては、基板上に順次に、陽極、正孔注入層、正孔輸送層、発光層兼電子輸送層、正孔阻止層、陰極からなるもの、また、陽極、正孔注入層、正孔輸送層、発光層、正孔阻止層、電子輸送層、電子注入層、陰極からなるものがあげられる。これらの多層構造においては、例えば、陽極、正孔注入層兼正孔輸送層兼発光層兼電子輸送層、正孔阻止層、陰極からなるものように、何層かの有機層の機能を兼用することによって、有機層の数を少なくすることができる。また、本発明の有機ＥＬ素子は、上記以外の新たな機能層を有してもよい。
本発明の陽極としては、ＩＴＯ、ＮＥＳＡ、酸化スズのような仕事関数の大きな電極材料が用いられる。正孔注入層としては、本発明のアリールアミン化合物や高分子材料の塗膜を用いる。この塗膜の上に低分子材料を蒸着したり、高分子材料を重ねて塗布することによって、正孔輸送層や発光層などを積層することができる。高分子材料の例としては、ＰＥＤＯＴ／ＰＳＳや、正孔輸送性の芳香族アミンを側鎖または主鎖に有する重合性の高分子などがあげられる。
また、銅フタロシアニン（以後、ＣｕＰｃと略称する）やスターバースト型のトリフェニルアミン誘導体、ナフタレンアミン化合物などの材料を蒸着して用いることができる。
正孔輸送層としては、本発明のアリールアミン化合物のほか、ベンジジン誘導体であるＮ，Ｎ’−ジフェニル−Ｎ，Ｎ’−ジ（ｍ−トリル）ベンジジン（以後、ＴＰＤと略称する）やＮ，Ｎ’−ジフェニル−Ｎ，Ｎ’−ジ（α−ナフチル）ベンジジン（以後、ＮＰＤと略称する）、種々のトリフェニルアミンの２量体や３量体、４量体を用いることができる。
本発明の発光層、あるいは電子輸送層としては、本発明のアリールアミン化合物に発光材料や電子輸送材料を混合したものや、高分子材料に電子輸送材料を混合したものを用いることができる。高分子材料の例としては、ポリジアルキルフルオレン誘導体、ポリ（Ｎ−ビニルカルバゾール）（以後、ＰＶＫと略称する）、ポリアニリン、ポリチオフェン、ポリ（ｐ−フェニレンビニレン）、ポリシロキサンなどがあげられる。また、各種の発光材料や、カルバゾール誘導体、キノリンのアルミ錯体、オキサゾール誘導体などの電子輸送材料を用いることができる。
また、発光層に例えば、キナクリドン、クマリン６、ルブレンなどの蛍光色素、あるいはフェニルピリジンのイリジウム錯体などの燐光発光材料など、ドーパントと称されている発光材料を添加することや、オキサゾール誘導体、トリアゾール誘導体などの電子輸送材料を添加することによって、本発明の有機ＥＬ素子の性能を高めることができる。
本発明の有機ＥＬ素子は正孔阻止層や電子注入層を有していても良い。正孔阻止層としてはバソクプロインやオキサゾール誘導体などを用いることができる。電子注入層としてはフッ化リチウムなどを用いることができる。本発明の陰極としては、マグネシウム、カルシウム、アルミニウムなどの金属、およびそれらのうち１つ以上と銀やインジウムなどとの合金のような仕事関数の小さな電極材料が用いられる。The molecular weight of the arylamine compound and derivative thereof of the present invention is preferably from 1500 to 6000. As described above, the reason why the lower limit of the molecular weight is determined in the present invention is that when the molecular weight is smaller than 1500, a stable thin film cannot be formed by coating, or defects such as crystallization are caused when the produced organic EL element is driven. Because it causes. On the other hand, the reason why the molecular weight is 6000 or less is that it is difficult to separate and separate compounds having different molecular weights during chemical synthesis.
The arylamine compound of the present invention having a molecular weight of 1500 or more and 6000 or less can be synthesized by condensing an arylamine and an aryl halide by the Ullmann reaction or the like.
Specific examples of preferable compounds among the arylamine compounds represented by the general formula (1) are shown below, but the present invention is not limited to these compounds.

As the “diarylamino structure-containing group”, as shown in the above exemplary compound, a 4- (diarylamino) phenyl group, a partial phenyl group constituting the 4- (diarylamino) phenyl group, or The thing which has a substituent in a phenylene group is mentioned. In addition, in this specification, “triphenylamine-like partial structure” refers to an unsubstituted triphenylamine structure, a triphenylamine structure having a substituent, and compounds of the above formulas (4) and (6). The terminal structure which has is included.
The compound of the present invention was purified by purification by column chromatography, recrystallization with a solvent, crystallization method or the like. It could be purified to single molecular species by column purification. The structure of the compound was identified by elemental analysis. One of the characteristics of the compound of the present invention is that it is composed of a single molecular species, not a mixture of various molecular species such as a polymer material, despite its large molecular weight.
As means for demonstrating that it is a single molecular species, the present inventors have used a time-of-flight mass spectrometer (hereinafter abbreviated as TOF-MS) that ionizes a compound and detects the potential difference space by drifting. Using. The analysis results using TOF-MS demonstrate the homogeneity of the compounds used in the present invention. Since it is a high-purity single molecular species, there are few carrier traps due to impurities that are the cause of durability deterioration of the organic EL element, and it is suitable as an organic layer constituting the organic EL element.
As physical properties of the compound, DSC measurement (Tg) and melting point were measured. The melting point is an index of vapor deposition, and the glass transition point (Tg) is an index of stability in a thin film state. Melting | fusing point and glass transition point were measured using the differential scanning calorimetry apparatus made from Mac Science using powder.
The work function was measured using an atmospheric photoelectron spectrometer AC2 manufactured by Riken Keiki Co., Ltd. after a 100 nm thin film was formed on the ITO substrate. The work function is an index of hole injection ability.
The compound of the present invention can produce an organic EL device by preparing a coating solution and forming a thin film by coating. A solvent such as cyclohexane, THF, trichloroethane, or o-dichlorobenzene is suitable for the solvent used for preparing the coating solution. Functional compounds such as a light emitting material and an electron transport material can be mixed in the coating solution.
As a film forming method using a coating solution, a spin coating method, a casting method, a micro gravure method, a gravure coating method, a bar coating method, a roll coating method, a wire bar coating method, a dip coating method, a spray coating method, a screen printing method, Coating methods such as a flexographic printing method, an offset printing method, and an ink jet printing method can be used.
The thickness of the coating film can be selected so that the driving voltage and durability of the organic EL element are optimized. At least a thickness that does not cause pinholes is required. If the thickness is too large, the driving voltage of the organic EL element increases, which is not preferable. Therefore, the film thickness of the coating film is, for example, 1 nm to 1 μm, preferably 10 to 200 nm.
As the structure of the organic EL device of the present invention, the substrate is composed of an anode, a hole injection layer, a hole transport layer, a light emitting layer / electron transport layer, a hole blocking layer, and a cathode sequentially on a substrate, Examples include a hole injection layer, a hole transport layer, a light emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer, and a cathode. In these multilayer structures, for example, the functions of several organic layers are also used such as an anode, a hole injection layer / hole transport layer / light emitting layer / electron transport layer, a hole blocking layer, and a cathode. As a result, the number of organic layers can be reduced. Moreover, the organic EL element of this invention may have a new functional layer other than the above.
As the anode of the present invention, an electrode material having a large work function such as ITO, NESA, or tin oxide is used. As the hole injection layer, a coating film of the arylamine compound or the polymer material of the present invention is used. By depositing a low molecular material on the coating film or applying a polymer material in layers, a hole transport layer, a light emitting layer, or the like can be laminated. Examples of the polymer material include PEDOT / PSS and a polymerizable polymer having a hole transporting aromatic amine in a side chain or main chain.
Further, materials such as copper phthalocyanine (hereinafter abbreviated as CuPc), starburst type triphenylamine derivatives, naphthaleneamine compounds, and the like can be used by vapor deposition.
As the hole transport layer, in addition to the arylamine compound of the present invention, N, N′-diphenyl-N, N′-di (m-tolyl) benzidine (hereinafter abbreviated as TPD), N, N′-diphenyl-N, N′-di (α-naphthyl) benzidine (hereinafter abbreviated as NPD), various diphenylamines, trimers and tetramers of triphenylamine can be used.
As the light emitting layer or the electron transport layer of the present invention, a mixture of the arylamine compound of the present invention with a light emitting material or an electron transport material, or a polymer material mixed with an electron transport material can be used. Examples of the polymer material include polydialkylfluorene derivatives, poly (N-vinylcarbazole) (hereinafter abbreviated as PVK), polyaniline, polythiophene, poly (p-phenylene vinylene), polysiloxane, and the like. In addition, various light-emitting materials, electron transport materials such as a carbazole derivative, an aluminum complex of quinoline, and an oxazole derivative can be used.
In addition, for example, a luminescent material called a dopant, such as a fluorescent dye such as quinacridone, coumarin 6, or rubrene, or a phosphorescent material such as an iridium complex of phenylpyridine, or an oxazole derivative or a triazole derivative is used. The performance of the organic EL device of the present invention can be enhanced by adding an electron transport material such as.
The organic EL device of the present invention may have a hole blocking layer or an electron injection layer. As the hole blocking layer, bathocuproin, an oxazole derivative, or the like can be used. As the electron injection layer, lithium fluoride or the like can be used. As the cathode of the present invention, an electrode material having a small work function such as a metal such as magnesium, calcium or aluminum and an alloy of one or more of them with silver or indium is used.

Embodiments of the present invention will be specifically described below with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist.
Example 1
(Synthesis of 4,4 ′, 4 ″ -tris [N, N-bis (4′-diphenylaminobiphenyl-4-yl)] triphenylamine (hereinafter abbreviated as TPA-9) (2))
While stirring 12.4 g of acetamide, 45.0 g of 4-iodo-4′-diphenylaminobiphenyl, 20.9 g of potassium carbonate, 2.0 g of copper powder, 1.1 g of sodium hydrogen sulfite and 15 ml of diphenyl ether under a nitrogen atmosphere, 210 The reaction was carried out at 0 ° C. for 10 hours. After completion of the reaction, 400 ml of toluene was added and stirred for 1 hour, followed by hot filtration, and the filtrate was concentrated to obtain crude crystals of acetyl. To the crude crystals, 220 ml of isopropyl alcohol and 11.8 g of potassium carbonate were added and refluxed for 7 hours. The reaction solution was concentrated to obtain a crude deacetylated product. The dried crude product was purified by column chromatography to obtain 11.6 g of white powder of N, N-bis- (4′-diphenylaminophenyl-4-yl) amine.
To 7 ml of dehydrated toluene, 1.00 g of N, N-bis (4′-diphenylaminophenyl-4-yl) amine, 0.23 g of tris (4-bromophenyl) amine, 0.26 g of sodium tertiary butoxide, palladium acetate ( II) 0.02 g and 0.003 g of sodium hydrogen sulfite were added and heated. Under reflux, a solution of tritertiary butylphosphine dissolved in 3 ml of dehydrated toluene was added and reacted for 4 hours.
After completion of the reaction, 60 ml of toluene was added and stirred for 1 hour, followed by hot filtration. After allowing to cool, the precipitate in the filtrate was filtered again to obtain a crude product. The dried crude product was purified by column chromatography (carrier: silica gel, eluent: chloroform / hexane = 5/3) to obtain 0.33 g (yield 31%) of TPA-9.
After the purification, the chemical structure of the obtained white powder was identified by elemental analysis. The results of elemental analysis were as follows.
Theoretical value (carbon 88.17%) (hydrogen 5.94%) (nitrogen 6.35%)
Actual value (carbon 87.85%) (hydrogen 5.98%) (nitrogen 6.17%)
The identified compounds were analyzed using MALDI-TOF-MS (Perspective Biosystem Inc., Department of Functional Polymers, Shinshu University), which is a mass spectrometer. The measurement result of TOF-MS is shown in FIG. 1, and the enlarged view is shown in FIG.
From the results of TOF-MS, it was confirmed that TPA-9 is an isotope group having a single chemical structure having a molecular weight such as 2206, 2207, 2205, 2208, and 2210. From the above results, it is clear that the compound of the present invention is highly pure and homogeneous despite having a high molecular weight of 1500 or more.
Example 2
(4,4 ′, 4 ″ -tris [N, N-bis (4′-diphenylamino-3,3′-dimethylbiphenyl-4-yl) amino] triphenylamine (hereinafter abbreviated as DM-TPA-9) ) (Synthesis of (3))
1. 150 g of dehydrated toluene, 10 g of N, N-bis (4′-diphenylamino-3,3′-dimethylbiphenyl-4-yl) amine, 2.18 g of tris (4-bromophenyl) amine, tertiary butoxy sodium 6 g and 0.015 g of palladium (II) acetate were added and heated to 60 ° C., and then 0.055 g of tritertiary butylphosphine was added and reacted at 95 ° C. for 11 hours.
After completion of the reaction, 100 ml of toluene was added and stirred for 1 hour, then allowed to cool to 45 ° C. and filtered hot. The filtrate was concentrated to obtain 19 g of a crude product. The dried crude product was purified by column chromatography (carrier: silica gel, eluent: toluene / hexane = 1/1), and 3.53 g (yield 32%, melting point 220.0-222) of DM-TPA-9. .5 ° C.).
Example 3
(4,4 ′, 4 ″ -Tris {N, N-bis [4 ′-(carbazol-9-yl) biphenyl-4-yl] amino} triphenylamine (hereinafter abbreviated as CZ-TPA-9) Synthesis of (4))
To 200 ml of dehydrated toluene, 10 g of N, N-bis [4 ′-(carbazol-9-yl) biphenyl-4-yl] amine, 2.4 g of tris (4-bromophenyl) amine, 2.85 g of tertiary butoxy sodium, After adding 0.017 g of palladium (II) acetate and heating to 60 ° C., 0.06 g of tritertiary butylphosphine was added and reacted at 95 ° C. for 12 hours.
After completion of the reaction, 100 ml of toluene was added and stirred for 1 hour, then allowed to cool to 45 ° C. and filtered hot. The filtrate was concentrated to obtain 33 g of a crude product. The dried crude product was put in 200 ml of toluene and stirred for 1 hour under reflux, followed by filtration. The residue was dissolved in 200 ml of THF and the insoluble matter was removed by filtration. Then, the filtrate was dropped into 300 ml of methanol to precipitate crystals, and 2.55 g (yield 24%, melting point) of CZ-TPA-9. 249.5-252.0 ° C.).
Example 4
(1 ′, (1 ′) ′, (1 ′) ″-tris [N, N-bis (4′-diphenylaminobiphenyl-4-yl) amino] -tris-4,4′-biphenylamine (hereinafter, (Abbreviated as BP-TPA-9) (Synthesis of (5))
To 50 ml of dehydrated toluene, 3.6 g of N, N-bis (4′-diphenylaminobiphenyl-4-yl) -4-bromoaniline, 0.5 g of triphenylamine-4,4 ′, 4 ″ -boronic acid, 2M After 2.6 ml of sodium carbonate was added, 0.023 g of tetrakis (triphenylphosphine) palladium (0) was added under a nitrogen stream and reacted at 85 ° C. for 96 hours.
After completion of the reaction, 100 ml of toluene was added and stirred at 80 ° C. for 1 hour, then allowed to cool to 45 ° C., and the reaction solution was transferred to a separatory funnel. The toluene layer was washed with water and then transferred to an eggplant flask, and 30 ml of the solvent was concentrated to precipitate crystals. The crystals were filtered and the crude product was dissolved in 30 ml of THF and added dropwise to 60 ml of toluene at room temperature to precipitate crystals. 0.42 g of BP-TPA-9 (yield 12.7%, melting point 222.0-225) 0.0 ° C).
The chemical structure of the white powder purified by repeating crystallization twice was identified by elemental analysis. The results of elemental analysis were as follows.
Theoretical value (carbon 88.78%) (hydrogen 5.46%) (nitrogen 5.75%)
Actual value (carbon 89.09%) (hydrogen 5.74%) (nitrogen 5.68%)
Example 5
About the compound and MTDATA of this invention, the glass transition point was calculated | required with the differential scanning calorimeter (made by Mac Science). The measurement results are as follows, and it was confirmed that the compound of the present invention has a remarkably high glass transition point.
TPA-9 Glass transition point: 188 ° C
DM-TPA-9 Glass transition point: 173 ° C
CZ-TPA-9 Glass transition point: 221 ° C
BP-TPA-9 Glass transition point: 204 ° C
MTDATA Glass transition point: 76 ° C
Example 6
After the TPA-9 (2) of the present invention was dissolved in 1,1,2-trichloroethane at a concentration of 2% by mass on an ITO substrate, the coating solution was coated by a spin coating method, and the coating was performed at 100 ° C. in a vacuum oven. A hole injection layer having a thickness of about 20 nm was formed by drying. By observation with a polarizing microscope, it was observed that the compound of the synthesis example of the present invention was a uniform and defect-free thin film.
Example 7
About the thin film of the compound of this invention produced by application | coating, the work function was measured with the atmospheric photoelectron spectroscopy apparatus (the Riken Keiki make, AC2). The measurement results are shown below.
TPA-9 work function: 5.06 eV
DM-TPA-9 Work function: 5.07 eV
CZ-TPA-9 Work function: 5.26 eV
BP-TPA-9 Work function: 5.21 eV
From the above results, it can be said that the thin film produced using the compound used in the organic EL device of the present invention has an energy level suitable as a hole injection / transport layer.
Example 8
As shown in FIG. 3, the organic EL element has a hole injection layer 3, a hole transport layer 4, a light emitting layer / electron transport layer on a glass substrate 1 on which an ITO electrode is previously formed as a transparent anode 2. 5 and a cathode (aluminum magnesium electrode) 7 were laminated in this order.
The glass substrate 1 on which ITO having a thickness of 150 nm was formed was cleaned with an organic solvent, and then subjected to oxygen plasma treatment to clean the surface.
On the ITO substrate, a coating solution of TPA-9 (2) dissolved in 1,1,2-trichloroethane is applied by spin coating, and dried at 100 ° C. in a vacuum oven to inject about 20 nm holes. Layer 3 was deposited. This was attached in a vacuum vapor deposition machine and depressurized to 0.001 Pa or less.
Subsequently, as the hole transport layer 4, TPD was formed to a thickness of about 30 nm at a deposition rate of 0.6 Å / s. Next, about 50 nm of Alq was formed as the light emitting layer / electron transport layer 5 at a deposition rate of 0.6 輸送 / s. The vapor deposition so far was continuously performed without breaking the vacuum. Finally, a cathode deposition mask was inserted, and an MgAg alloy was deposited at a ratio of 10: 1 to about 200 nm to form the cathode 7. The produced device was stored in a vacuum desiccator, and the characteristics were measured at room temperature in the air.
The characteristics of the organic EL device of the present invention formed as described above were increased when the current density was loaded with a current density of 400 mA / cm ² , the light emission efficiency defined by the light emission brightness / voltage, and the current density load further increased. The maximum brightness before breakthrough was evaluated. Since the maximum luminance measured by this method reflects the electrical stability of the element, it is an index of the durability of the organic EL element.
When a current density of 400 mA / cm ² was loaded on the organic EL element, stable green light emission of 25000 cd / m ² was obtained. The luminous efficiency at this luminance was as high as 5.10 cd / A. The element voltage at this time was 14.0V. When the load was further increased, the maximum luminance was 21000 cd / m ² and the device deteriorated.
Comparative Example 1
For comparison, the material of the hole injection layer 3 was replaced with MTDATA and the characteristics thereof were examined. Since MTDATA cannot produce a uniform and defect-free thin film by coating, the thin film was produced by vapor deposition. That is, the ITO substrate was mounted in a vacuum vapor deposition machine and the pressure was reduced to 0.001 Pa or less, and MTDATA was formed as the hole injection layer 3 at a deposition rate of 0.6 Å / s to about 20 nm. Subsequently, as in Example 5, the hole transport layer, the light emitting layer / electron transport layer, and the cathode were all formed by vapor deposition. These vapor depositions were continuously performed without breaking the vacuum.
When the load current density of 400 mA / cm ² to the organic EL device using MTDATA, green light 15300cd / ^{m 2} was obtained. The luminous efficiency at this luminance was 3.90 cd / A. The element voltage at this time was 14.8V. When the load was further increased, the maximum luminance of 16000 cd / m ² was shown and the device deteriorated.
Comparative Example 2
For further comparison, the material of the hole injection layer 3 was replaced with copper phthalocyanine, and the characteristics were examined. In place of MTDATA in Comparative Example 1, purified copper phthalocyanine was formed to a thickness of about 20 nm at a deposition rate of 4 nm / min. Subsequently, an element was produced in the same manner as in Comparative Example 1.
When a current density of EL element 400 mA / cm ² using copper phthalocyanine was loaded, green light emission of 16200 cd / m ² was obtained. The luminous efficiency at this luminance was 4.12 cd / A. The element voltage at this time was 12.4V. When the load was further increased, the maximum luminance was 18000 cd / m ² and the device deteriorated.
From the above results, it is clear that the light emitting efficiency and durability of the organic EL device of the present invention are superior to the conventional organic EL device.
Example 9
As shown in FIG. 4, the organic EL element has a hole injection layer / hole transport layer 3 and 4 and a light emitting layer / electron transport layer on an ITO electrode previously formed on a glass substrate 1 as a transparent anode 2. 5 and a cathode (aluminum magnesium electrode) 7 were laminated in this order. The glass substrate 1 on which ITO with a film thickness of 150 nm was formed was cleaned with an organic solvent, and then subjected to oxygen plasma treatment to clean the surface.
As in Example 8, TPA-9 (2) was coated on the ITO substrate by spin coating, and dried in a vacuum oven to form hole injection / hole transport layers 3 and 4 of about 50 nm. Filmed. This was attached in a vacuum vapor deposition machine and depressurized to 0.001 Pa or less. Next, about 50 nm of Alq was formed as the light emitting layer / electron transport layer 5 at a deposition rate of 0.6 輸送 / s. Finally, a cathode deposition mask was inserted, and an MgAg alloy was deposited to form the cathode 7.
When a current density of 400 mA / cm ² was applied to the organic EL element, stable green light emission of 8100 cd / m ² was obtained.
Example 10
A device in which a hole blocking layer was laminated between the light emitting layer / electron transport layer 5 and the cathode (aluminum magnesium electrode) 7 as shown in FIG. 5 was produced. An organic EL element is formed by laminating a hole injection layer / hole transport layer 3 and 4 and a light emitting layer / electron transport layer 5 as a coating film, and laminating a hole blocking layer 6 and a cathode thereon by vapor deposition. It was produced by. That is, as in Example 8, TPA-9 (2) was coated on the ITO substrate by spin coating and dried in a vacuum oven to form hole injection / hole transport layers 3 and 4 having a thickness of about 20 nm. A film was formed.
Subsequently, a coating solution of PVK [PVK and 2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole (hereinafter abbreviated as PBD), coumarin 6 10: 3: 0.2 dissolved in o-dichlorobenzene] by a spin coating method and dried at 100 ° C. in a vacuum oven to form a light emitting layer / electron transport layer 5 having a thickness of about 70 nm. did. Next, bathocuproine (hereinafter abbreviated as BCP) was deposited to form the hole blocking layer 6. Finally, a cathode deposition mask was inserted, and an MgAg alloy was deposited to form the cathode 7.
When a current density of 300 mA / cm ² was applied to the organic EL device thus produced, stable green light emission of 2800 cd / m ² was obtained.
Example 11
As shown in FIG. 6, the organic EL element has a hole injection layer / hole transport layer / light emitting layer / electron transport layer 3, 4 on a glass substrate 1 on which an ITO electrode is previously formed as a transparent anode 2. And 5 were made of a coating film, and the hole blocking layer 6 and the cathode (aluminum magnesium electrode) 7 were laminated by vapor deposition.
A TPA-9 (2) coating solution (PVK and PBD, coumarin 6 dissolved in 1,1,2-trichloroethane at a ratio of 10: 3: 0.2) on an ITO substrate by spin coating. The coated film was dried at 100 ° C. in a vacuum oven to form a hole injection layer / hole transport layer / light emitting layer / electron transport layer 3, 4 and 5 having a thickness of about 70 nm. Next, BCP was deposited to form a hole blocking layer 6. Finally, a cathode deposition mask was inserted, and an MgAg alloy was deposited to form the cathode 7.
When a voltage of 6.3 V was applied to the organic EL element, stable green light emission of 400 cd / m ² was obtained.
From the above results, it is apparent that the organic EL device produced using the arylamine compound of the present invention is superior in light emission characteristics and durability to conventional organic EL devices.
Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.
This application is based on a Japanese patent application filed on March 25, 2004 (Japanese Patent Application No. 2004-089836) and a Japanese patent application filed on March 25, 2004 (Japanese Patent Application No. 2004-090334). Incorporated herein by reference.

  The arylamine compound having a molecular weight of 1500 or more and 6000 or less of the present invention is excellent as a compound for an organic EL device because it has a high amorphous property and can form a thin film by coating and has a stable thin film state. By producing an organic EL device using the thin film coated with the arylamine compound of the present invention as a hole injection layer or a hole transport layer, the luminous efficiency and durability of the conventional coating type organic EL device are remarkably increased. It can be improved. For example, it has become possible to develop home appliances and lighting.

Claims (8)

An arylamine compound having a molecular weight of 1500 to 6000 represented by the following general formula (1).

(In the formula, X represents a single bond, CH or CH ₂ , or N or NH, Ar ₁ , Ar ₂ , and Ar ₃ represent a phenyl group, a biphenyl group, or a terphenyl group, and R ₁ , R ₂ , R 3 ₃ , R ₄ , R ₅ and R ₆ each independently represents an aryl group, and this aryl group may be further substituted with a diarylamino group so as to form a triphenylamine partial structure. The group may be substituted with a diarylamino structure-containing group so as to form a triphenylamine-like partial structure repeatedly, and n represents 0 or 1.)   The arylamine compound according to claim 1, which has 9 or 10 nitrogen atoms in the molecule.   The arylamine compound according to claim 2, having 10 nitrogen atoms in the molecule.   The arylamine compound according to any one of claims 1 to 3, wherein the arylamine compound has 7 to 9 triphenylamine-like partial structures in the molecule. In an organic electroluminescence device having at least one organic layer sandwiched between a pair of electrodes, an arylamine compound having a molecular weight of 1500 to 6000 represented by the following general formula (1) is formed of at least one organic layer. An organic electroluminescence element contained as a material.

(In the formula, X represents a single bond, CH or CH ₂ , or N or NH, Ar ₁ , Ar ₂ , and Ar ₃ represent a phenyl group, a biphenyl group, or a terphenyl group, and R ₁ , R ₂ , R 3 ₃ , R ₄ , R ₅ and R ₆ each independently represents an aryl group, and this aryl group may be further substituted with a diarylamino group so as to form a triphenylamine partial structure. The group may be substituted with a diarylamino structure-containing group so as to form a triphenylamine-like partial structure repeatedly, and n represents 0 or 1.)   The organic electroluminescence device according to claim 5, wherein the arylamine compound has 9 or 10 nitrogen atoms in the molecule.   The organic electroluminescent device according to claim 6, wherein the arylamine compound has 10 nitrogen atoms in the molecule.   The organic electroluminescence device according to any one of claims 5 to 7, wherein the arylamine compound has 7 to 9 triphenylamine-like partial structures in a molecule.

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