JP5374833B2 - Organic electroluminescent material and organic electroluminescent device using the same - Google Patents

Description

  The present invention relates to an organic electroluminescent material having a reduced impurity concentration and an organic electroluminescent element using the same.

  Hereinafter, electroluminescence is abbreviated as EL.

  Organic EL devices have been intensively studied as light-emitting devices with high-speed response, high viewing angle, and high efficiency, and have recently been put into practical use. However, it is still not at a satisfactory level in terms of life and efficiency, and development aimed at further long life and high efficiency continues.

  The deterioration of the organic EL element which is a particular problem requires further improvement. Recently, it has been reported that impurities in the material are greatly influenced as a cause of deterioration in initial luminance of the organic EL element and deterioration over time (for example, see Patent Documents 1 to 6).

  In particular, Patent Document 6 describes the use of impurities derived from raw materials used in manufacturing these materials, intermediates or precursors generated in the manufacturing process, and halogen compounds as impurities in organic EL materials. The unreacted product as an intermediate is described. It is described that high-performance liquid chromatography is a good method for quantifying impurities.

  Patent Document 3 describes impurities that may be generated by cross-coupling reactions, for example, homo-coupled bodies bonded between the same reactive species, and those in which halogen atoms or metal atoms of raw materials are replaced with hydrogen. Yes. The quantitative method is also high performance liquid chromatography.

JP 2002-235077 A (Claims) JP 2002-373785 A (Claims) JP 2002-373786 A (Claims) JP 2003-68467 A (Claims) JP-A-2005-225916 (Claims) WO2000 / 41443 (Claims)

  In the organic EL material having the organic group represented by the above general formula (1) or (2) showing a high efficiency as a partial structure, it is found that there are impurities that cannot be quantified by conventional analysis of impurities by high performance liquid chromatography. I came. For example, even though high-performance liquid chromatography analysis shows the same purity, the evaluation with an EL element has considerably different color purity and life, and there may be variations in EL performance between lots. Unless the behavior of impurities is analyzed, it has been found that high-efficiency and long-life devices cannot be manufactured stably.

  An object of the present invention is to provide an organic EL material having, as a partial structure, an organic group represented by the above general formula (1) or (2) with few impurities, and an organic EL element using the same.

  As a result of intensive studies, the present inventors have found that in an organic EL material having an organic group represented by the general formula (1) or (2) as a partial structure, the fluorescence intensity at the maximum fluorescence wavelength (λmax) of the fluorescence spectrum in a thin film The organic EL material characterized in that the ratio of the fluorescence intensity at (λmax + 60 nm) with respect to is less than 0.2 is found to be very excellent in terms of efficiency and suppression of deterioration of the device, and the present invention is completed. It came.

  That is, the present invention has an organic group represented by the following general formula (1) or (2) as a partial structure, and the fluorescence at (λmax + 60 nm) with respect to the fluorescence intensity at the maximum fluorescence wavelength (λmax) of the fluorescence spectrum in the thin film. The present invention relates to an organic EL material having an intensity ratio of less than 0.2 and its use.

（式中、Ｒ^１，Ｒ^２は各々独立して炭素数１〜８のアルキル基、または炭素数６〜１２のアリール基を表す。なお、Ｒ^１とＲ^２は結合して環を形成してもよい。）
上記一般式（１）または（２）で表される有機基を部分構造として有する有機ＥＬ材料は、下記一般式（３）または（４）で表されるハロゲン化合物と、銅，パラジウムおよびニッケルのような遷移金属触媒存在下、有機金属化合物とのクロスカップリング反応、パラジウム触媒を用いたアミン化合物とのＢｕｃｈｗａｌｄ−Ｈａｒｔｗｉｇ反応（例えば、Ｊｏｕｒｎａｌ ｏｆ ｃｈｅｍｉｓｔｒｙ，６５，１１５８−１１７４（２０００）参照）、銅触媒を用いたアミン化合物とのＵｌｌｍａｎｎ反応等から合成することができる。

(Wherein R ¹ and R ² each independently represents an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 12 carbon atoms. R ¹ and R ² are bonded to form a ring. May be.)
The organic EL material having the organic group represented by the general formula (1) or (2) as a partial structure is composed of a halogen compound represented by the following general formula (3) or (4), and copper, palladium and nickel. In the presence of such a transition metal catalyst, a cross-coupling reaction with an organometallic compound, a Buchwald-Hartwig reaction with an amine compound using a palladium catalyst (see, for example, Journal of chemistry, 65, 1158-1174 (2000)), copper It can be synthesized from a Ullmann reaction with an amine compound using a catalyst.

（式中、Ｘ^１，Ｘ^２は各々独立して水素原子、臭素原子、塩素原子またはヨウ素原子であり、少なくともいずれかはハロゲン原子である。また、Ｒ^１，Ｒ^２は各々独立して炭素数１〜８のアルキル基、または炭素数６〜１２のアリール基を表す。なお、Ｒ^１とＲ^２は結合して環を形成してもよい。）
ここで言うクロスカップリング反応とは、炭素−炭素結合を生成する反応であり、有機ホウ素化合物を用いた鈴木−宮浦反応（例えば、Ｔｅｔｒａｈｅｄｒｏｎ，５８，９６３３−９６９５（２００２）参照）、有機スズ化合物を用いたＳｔｉｌｌ反応、有機亜鉛化合物を用いたＮｅｇｉｓｈｉ反応等（例えば、Ｐａｌｌａｄｉｕｍ Ｒｅａｇｅｎｔｓ ａｎｄ Ｃａｔａｌｙｓｔｓ（２００４） Ｊｏｈｎ Ｗｉｌｅｙ ＆ Ｓｏｎｓ，Ｌｔｄ．参照）が挙げられる。

(In the formula, X ¹ and X ² are each independently a hydrogen atom, bromine atom, chlorine atom or iodine atom, and at least one is a halogen atom. Also, R ¹ and R ² are each independently carbon. Represents an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 12 carbon atoms, wherein R ¹ and R ² may combine to form a ring.
The cross-coupling reaction referred to here is a reaction that generates a carbon-carbon bond, and is a Suzuki-Miyaura reaction using an organic boron compound (see, for example, Tetrahedron, 58, 9633-9695 (2002)), an organic tin compound. Still reaction using an organic zinc compound, Negishi reaction using an organic zinc compound, and the like (see, for example, Palladium Reagents and Catalysts (2004) John Wiley & Sons, Ltd.).

  The conditions during these reactions are not particularly limited. However, the metal residue derived from the transition metal catalyst used in these reactions should be as small as possible. The amount of the transition metal catalyst is 0 with respect to 1 mol of the halogen compound represented by the general formula (3) or (4). 0.5 mol% or less, more preferably 0.2 mol% or less.

  Further, the organic EL material represented by the above general formula (1) or (2) obtained by such a known method can be purified by chromatography such as silica gel, alumina and activated clay, recrystallization, sublimation purification and the like. It refine | purifies by using in combination.

  Examples of organic EL materials to be synthesized are shown below, but are not particularly limited to these compounds.

上記化合物は、下記一般式（５）〜（８）または（９）〜（１１）で表されるフェニルナフタレン誘導体の環化反応を経由して合成できる。

The said compound is compoundable via the cyclization reaction of the phenyl naphthalene derivative represented by the following general formula (5)-(8) or (9)-(11).

（式中、Ｘ^１，Ｘ^２は各々独立して水素原子、臭素原子、塩素原子またはヨウ素原子であり、少なくともいずれかはハロゲン原子である。また、Ｒ^３〜Ｒ^６は各々独立して炭素数１〜８のアルキル基、または炭素数６〜１２のアリール基を表す。なお、Ｒ^３とＲ^４またはＲ^５とＲ^６は結合して環を形成してもよい。）
上記一般式（５）〜（８）の環化反応は、酸触媒、有機溶媒中で実施される。酸触媒としては、ブレンステッド酸またはルイス酸であり、好ましくはルイス酸である。ルイス酸の具体例としては、塩化鉄（ＩＩＩ）、臭化鉄（ＩＩＩ）等の鉄化合物、塩化亜鉛、臭化亜鉛等の亜鉛化合物、塩化ジルコニウム等のジルコニウム化合物、塩化チタン、臭化チタン、チタニウムエトキシド等のチタン化合物、塩化アルミニウム、臭化アルミニウム等のアルミニウム化合物、三フッ化ホウ素、三フッ化ホウ素・エーテル錯体、三フッ化ホウ素・酢酸錯体、三臭化ホウ素等のホウ素化合物、塩化スカンジウム、塩化ランタン等のランタノイド金属塩等が挙げられる。中でもホウ素化合物が好ましい。

(In the formula, X ¹ and X ² are each independently a hydrogen atom, bromine atom, chlorine atom or iodine atom, and at least one is a halogen atom. Also, R ^{3 to} R ⁶ are each independently carbon. Represents an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 12 carbon atoms, and R ³ and R ⁴ or R ⁵ and R ⁶ may be bonded to form a ring.
The cyclization reaction of the general formulas (5) to (8) is carried out in an acid catalyst and an organic solvent. The acid catalyst is Bronsted acid or Lewis acid, preferably Lewis acid. Specific examples of Lewis acids include iron compounds such as iron (III) chloride and iron (III) bromide, zinc compounds such as zinc chloride and zinc bromide, zirconium compounds such as zirconium chloride, titanium chloride, titanium bromide, Titanium compounds such as titanium ethoxide, aluminum compounds such as aluminum chloride and aluminum bromide, boron trifluoride, boron trifluoride / ether complex, boron trifluoride / acetic acid complex, boron compounds such as boron tribromide, chloride And lanthanoid metal salts such as scandium and lanthanum chloride. Of these, boron compounds are preferred.

  The usage-amount of an acid catalyst is 0.1-20 times mol normally with respect to 1 mol of phenylnaphthalene derivatives represented by either of the said General formula (5)-(8). The organic solvent to be used is not particularly limited as long as it does not inhibit the reaction, but usually a halogen-based solvent such as dichloromethane, chloroform, carbon tetrachloride or the like is preferable.

  In addition, the cyclization reaction of the phenylnaphthalene derivatives represented by the general formulas (9) to (12) is performed in an organic solvent in the presence of a strong base (for example, Journal of Organic Chemistry, 56, 1683-1685). (1991)). Examples of the strong base include tert-butyl lithium and lithium diisopropylamide as described in the above-mentioned document. The organic solvent is not particularly limited as long as it does not inhibit the reaction, but usually ether solvents such as tetrahydrofuran and dioxane are preferable.

The corresponding benzofluorenone derivative is produced by the cyclization reaction of the phenylnaphthalene derivative represented by any one of the general formulas (9) to (12). For example, the general formula (3) or (4) (For example, R ³ , R ⁴ = phenyl) is synthesized through a known Grignard reaction and Friedel-Craft reaction (see the following formula (13)).

前述の環化反応により、９５％以上の純度で目的とする上記一般式（３）または（４）で表されるハロゲン化合物が得られる。しかし、このまま次工程のクロスカップリング反応および／またはアミノ化反応を経て、再結晶、クロマトグラフィーまたは昇華による精製を行っても、高純度の上記一般式（１）または（２）で表される有機基を部分構造として有する有機ＥＬ材料が得られないばかりか、素子特性でも良好な結果が得られない。

By the cyclization reaction described above, the desired halogen compound represented by the above general formula (3) or (4) is obtained with a purity of 95% or more. However, even if purification through recrystallization, chromatography, or sublimation is performed through the cross-coupling reaction and / or amination reaction of the next step as it is, it is represented by the general formula (1) or (2) with high purity. Not only an organic EL material having an organic group as a partial structure cannot be obtained, but also good results cannot be obtained in device characteristics.

  In particular, the organic EL materials synthesized by amination reaction (for example, the above exemplary compounds (A1) to (A6), (B1) to (B8), (C1) to (C6)) may have high apparent purity. In addition, the device characteristics, particularly the device life reduction rate is large.

The above-mentioned cyclization reaction products are very complex and not all can be identified. However, by mass spectrometry, other than the halogen compound represented by the general formula (3) or (4), for example, at the terminal The existence of a compound having an olefin group or a tertiary alkyl group, a dimerized compound, a polymerized viscous compound, or the like is suggested. These impurities are purified by a known method such as recrystallization and chromatography, and a halogen compound in which the impurity concentration in high performance liquid chromatography analysis is reduced to 0.5 area% or less is used for cross-coupling reaction and / or When comparing an organic EL material obtained by amination reaction with an organic EL material that is not, even if it shows the same purity by high performance liquid chromatography analysis, the spectrum of the long wavelength component is clearly in the fluorescence spectrum. It turned out to be different. The spectrum of the long wavelength component is different from the ratio of the fluorescence intensity at (λmax + 60 nm) to the fluorescence intensity at the maximum fluorescence wavelength (λmax) of the fluorescence spectrum in the thin film, that is, the fluorescence intensity _{λmax + 60} / fluorescence intensity _λmax is less than 0.2. Indicates whether or not there is. It was found that when an organic EL material satisfying that the fluorescence intensity _{λmax + 60} / fluorescence intensity _λmax is less than 0.2 is used, the efficiency and lifetime of the EL element are improved.

  In addition, the fluorescence spectrum in a thin film said here points out the fluorescence spectrum in powder.

As described above, since the fluorescence intensity _{λmax + 60} / fluorescence intensity _{λmax in} the thin film of the organic EL material having the organic group represented by the above (1) or (2) as a partial structure is less than 0.2, the efficiency is very high. -A long-life organic EL element becomes possible.

  The organic EL material having a partial structure of the organic group represented by the general formula (1) or (2) of the present invention is at least one of a hole injection layer, a hole transport layer, a light emitting layer, and an electron transport layer. Although used for the layer, a hole injection layer, a hole transport layer, and a light emitting layer are preferable.

  The organic EL material having the organic group represented by the above general formula (1) or (2) as a partial structure according to the present invention achieves further low voltage driving and high power efficiency, and in addition, durability of the organic EL element comprising the organic EL material. Can be expected.

  Hereinafter, the present invention will be described in more detail based on examples.

  High performance liquid chromatography (HPLC) analysis uses Tosoh LC-8020 series (CCPM-II type pump, UV-8020 type UV detector, CO-8020 type column oven), and acetonitrile: tetrahydrofuran as the moving bed. = 9: 1 (volume ratio), Inertsil ODS-3V (4.5 mm id × 250 mm) was used as an analytical column. The flow rate was 1 ml / min, the measurement wavelength was 254 nm, the column temperature was 45 ° C., and the injection volume was 5 μl.

  The fluorescence spectrum was measured under conditions of room temperature (in the air) and excitation wavelength of 340 nm using Hitachi F-2500 filled with a sample ground in an agate mortar.

¹ H-NMR measurement, ¹³ C-NMR measurement, and FDMS measurement were performed using Gemini 200 manufactured by Varian and M-80B manufactured by Hitachi, Ltd., respectively.

Synthesis example 1
2-Bromo-6- (2-hydroxyisopropyl) phenyl-naphthalene (26.7 g, 78 mmol) and chloroform (570 ml) were placed in a 1 l three-necked flask purged with nitrogen, and boron trifluoride / diethyl ether was added to the solution under a nitrogen stream. 14.5 g (102 mmol) of the complex was added dropwise over 10 minutes. After completion of dropping, the temperature was raised to 50 ° C. and stirred for 2 hours. After cooling to room temperature, it was separated and washed with pure water, and the resulting organic layer was dried over anhydrous magnesium sulfate. The residue obtained after concentration was purified by silica gel chromatography (hexane / toluene = 1/1 (volume ratio)) and then washed with hexane to obtain 13.5 g (yield 49%) as a yellow powder. The HPLC purity of the obtained powder was 99.4%. This sample is A.

  Furthermore, recrystallization was performed twice from a toluene / hexane = 1/1 (volume ratio) solution to obtain a colorless halogen compound with a purity of 99.7%. Let this sample be B.

Synthesis Example 2 (Synthesis of Compound [B7])
In a 100 ml eggplant-shaped flask, 3.0 g (9.3 mmol) of the halogen compound obtained in Synthesis Example 1 (9.3 mmol), 1.54 g (4.6 mmol) of N, N′-diphenylbenzidine, sodium-tert-butoxide 1.1 g (11.5 mmol) and 80 ml of xylene were introduced and suspended, and the system was replaced with nitrogen. Furthermore, under a nitrogen atmosphere, 4.2 mg (0.019 mmol, 0.2 mol%) of palladium acetate and 12 mg of tri-tert-butylphosphine were added and heated to 125 ° C. After aging at a predetermined temperature for 5 hours, the reaction solution was cooled to room temperature. After adding 40 ml of water, extraction was performed with dichloromethane, and the organic phase was washed with water and concentrated.

Comparative Example 1
The sample was synthesized according to Synthesis Example 2 using Sample A (HPLC purity 99.4%) of Synthesis Example 1. The obtained concentrated liquid was purified by silica gel column chromatography (toluene) and concentrated. Then, after melt | dissolving in 10 ml of toluene, it was dripped at the methanol solution prepared previously, and the produced | generated precipitation was filtered. By vacuum drying, 3.4 g of compound [B7] was obtained (purity 97.8%, yield 89%).

Further, 0.8 g was purified by sublimation at 340 ° C. × 10 ⁻³ Pa for 5 hours to obtain 0.67 g of Sample C. The purity by HPLC analysis was 99.3%. The fluorescence spectrum of the obtained compound [B7] is shown in FIG. The fluorescence intensity _{λmax + 60} / fluorescence intensity _λmax (hereinafter abbreviated as PL intensity ratio) was 0.26.

<Element fabrication>
A glass substrate having an ITO transparent electrode having a thickness of 130 nm was ultrasonically washed successively with acetone and isopropyl alcohol, then boiled and washed with isopropyl alcohol, and then dried. Furthermore, what was UV / ozone treated was used as a transparent conductive support substrate. On the ITO transparent electrode, copper phthalocyanine was formed into a film with a thickness of 25 nm by vacuum deposition. Next, the compound [B7] obtained in Comparative Example 1 was formed into a film with a thickness of 45 nm by a vacuum vapor deposition method to form a hole transport layer. Next, an aluminum triskinolinol complex was formed into a film with a thickness of 60 nm by a vacuum vapor deposition method to form an electron transport layer. The organic compound was deposited under the same conditions of a vacuum degree of 1.0 × 10 ⁻⁴ Pa and a deposition rate of 0.3 nm / second.

  Next, LiF was deposited to 0.5 nm and Al was deposited to 100 nm as a cathode to form a metal electrode.

Further, a protective glass substrate was stacked in a nitrogen atmosphere and sealed with a UV curable resin. The EL device thus obtained was evaluated for an EL device at a current density of 20 mA / cm ^{2 using} an ITO electrode as a positive electrode and a LiF-Al electrode as a negative electrode. The voltage and current efficiency at that time were 5.6 V and 4.5 cd / A, respectively. The luminance half life was 1000 hours. The results are shown in Table 1.

Comparative Example 2
The concentrate obtained by purification by silica gel chromatography in Comparative Example 1 was purified twice by silica gel chromatography again. Then, reprecipitation operation similar to the comparative example 1 was performed, and 3.2 g of compound [B7] was obtained (purity 98.1%, yield 86%).

Then, 1.0 g was sublimated and purified twice at 340 ° C. × 10 ⁻³ Pa to obtain 0.59 g of compound [B7]. The purity by HPLC analysis was 99.8%. An element similar to that of Comparative Example 1 was manufactured and an EL element was evaluated. The results are shown in Table 1.

Example 1
The target product was synthesized according to Synthesis Example 2 using Sample B of Synthesis Example 1 (HPLC purity 99.7%). The same operation as in Comparative Example 1 was performed to obtain 99.8% of compound [B7].

  An element similar to that of Comparative Example 1 was manufactured and an EL element was evaluated. The results are shown in Table 1.

Example 2
The product obtained in Example 1 was purified by sublimation again under the same conditions to obtain a sample having an HPLC purity of 99.9%. The fluorescence spectrum of the obtained compound [B7] is shown in FIG. The PL intensity ratio was 0.09. An element similar to that of Comparative Example 1 was manufactured and an EL element was evaluated. The results are shown in Table 1.

The fluorescence spectrum of compound [B7] obtained by the comparative example 1 and Example 2 is shown.

Claims (7)

It has an organic group represented by the following general formula (2) as a partial structure, and any one carbon atom at the 3-position, 7-position, 8-position, 9-position or 10-position on the condensed ring of the partial skeleton An organic group is bonded to the organic compound, and the ratio of the fluorescence intensity at (λmax + 60 nm) to the fluorescence intensity at the maximum fluorescence wavelength (hereinafter abbreviated as λmax) of the fluorescence spectrum in the thin film is 0.15 or less. Electroluminescent material.

(Wherein R ¹ and R ² each independently represents an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 12 carbon atoms. R ¹ and R ² are bonded to form a ring. May be.) The following general formula (2)

(Wherein R ¹ and R ² each independently represents an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 12 carbon atoms. R ¹ and R ² are bonded to form a ring. May be.)
The ratio of the fluorescence intensity at (λmax + 60 nm) to the fluorescence intensity at the maximum fluorescence wavelength (hereinafter abbreviated as λmax) of the fluorescence spectrum in the thin film is 0.15 or less, The following general formula (4)

(In the formula, X1 and X2 are each independently a hydrogen atom, bromine atom, chlorine atom or iodine atom, and at least one is a halogen atom. Also, R1 and R2 each independently have 1 to 8 carbon atoms. Or an aryl group having 6 to 12 carbon atoms, wherein R1 and R2 may combine to form a ring.)
Characterized in that it is obtained the in represented by halogen compound aminated organic electroluminescent material of claim 1. 3. The organic electroluminescent material according to claim 1, wherein a fluorescence intensity ratio of (λmax + 60 nm) to λmax is 0.09 or less. The organic electroluminescent material according to any one of claims 1 to 3, wherein R ¹ and R ² are each independently an alkyl group having 1 to 8 carbon atoms. . The organic electroluminescent element characterized by including at least one layer of the organic electroluminescent material as described in any one of Claims 1-4 as an organic compound layer between a pair of electrodes. The organic compound layer containing the organic electroluminescent material according to any one of claims 1 to 5 is any one of a light emitting layer, a hole transport layer, and a hole injection layer. The organic electroluminescent element of description. The following general formula (2)

(Wherein R ¹ and R ² each independently represents an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 12 carbon atoms. R ¹ and R ² are bonded to form a ring. May be.)
And an amino group is bonded to any one of the 3-position, 7-position, 8-position, 9-position, and 10-position on the condensed ring of the partial skeleton. An organic electroluminescent material having a ratio of the fluorescence intensity at (λmax + 60 nm) to the fluorescence intensity at the maximum fluorescence wavelength (hereinafter abbreviated as λmax) of the fluorescence spectrum of the thin film is 0.15 or less is used. , A method for extending the life of organic EL elements.

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