KR100681474B1 - Hexaphenylbenzenes with aminostyryl moiety for organic electroluminescent materials - Google Patents

Abstract

Provided is a novel blue fluorescence material, which has excellent stability, allows realization of a blue to green color in an organic electroluminescence device(OLED), and improves the efficiency of an OLED when used as a hole transport or light emitting material. The blue fluorescence material is an aminostyryl group-containing hexaphenylbenzene compound represented by the following formula (I). In the formula (1), R1 and R2 which are the same or different represent a C1-C4 alkyl, a substituted or non-substituted phenyl, naphthyl or anthracenyl group; and R3 is a hydrogen atom or is linked to R2 to form a heterocyclic compound.

Description

Hexaphenylbenzenes with aminostyryl moiety for organic electroluminescent materials}

1 is a view showing the structure of the organic electroluminescent device manufactured in the present invention,

2 to 4 show the nmr spectrum of the representative compound synthesized in the present invention,

5 to 7 show the fluorescence spectrum,

Figure 8 shows the current density-voltage characteristic curve comparing the compound and the device characteristics of the conventional compound by applying the compound synthesized in the present invention to the hole transport layer of the device

Figure 9 shows the luminous efficiency curve for the current density of the device produced by using the representative compound synthesized in the present invention as a light emitting layer material of the organic electroluminescent device.

BACKGROUND OF THE INVENTION An organic electroluminescent device (OLED) is one of a kind of electronic devices which place an organic semiconductor material between an electrode plate of an anode and a cathode and emit light of a specific color according to an applied current. An anode on a glass substrate is usually laminated with a transparent electrode called ITO and laminated in the order of a hole injection layer (HIL), a hole transport layer (HTL), a light emitting layer (EML), an electron transport layer (ETL), and a metal cathode. Tang et al., 1987, published in Applied Physics Letters, Vol. 51, pp. 913, described an organic electroluminescent device with good multi-layer structure.

In order for the organic electroluminescent device (OLED) to have a higher efficiency, it is necessary to achieve more balanced recombination of holes and electrons in the light emitting layer. Efforts have been made to obtain efficient light emission from organic electroluminescent devices (OLEDs). First, novel electron transfer materials having higher electron mobility and efforts to lower the electron injection barrier by modifying the cathode material are described in US Pat. Nos. 4,885,211 and 5,059,862 and 5,766,779, respectively. Meanwhile, US Pat. No. 6,603,150 to Tang et al. Has pursued a technical purpose of achieving more balanced recombination by stacking an interface layer between a hole transport layer and a light emitting layer.

SUMMARY OF THE INVENTION An object of the present invention is to provide novel compounds having blue light emitting properties in order to make organic electroluminescent devices (OLEDs) with improved efficiency, and to prepare these compounds and to include these compounds as hole transport materials or light emitting materials. It is to provide an organic electroluminescent device.

The purpose of the above

a) glass substrate;

b) ITO transparent anode;

c) a hole injection layer to a hole transport layer;

d) a light emitting layer;

e) an electron transport layer;

d) It is achieved by using a novel material represented by the following general structural formula (I), comprising the cathodes in order and as the hole transport material of the hole transport layer or the light emitting material of the light emitting layer.

Wherein R ₁ and R ₂ are the same or different from each other and represent C1 to C4 alkyl, substituted or unsubstituted phenyl, naphthyl or anthracenyl groups, and R ₃ is linked to hydrogen or R ₂ to form a heterocyclic compound.

-NPD등이 소자구동중의 안정성 측면에서 미흡할정도의 정공전달 특성으로 인해 발광층에서 효과적인 정공,전자 재결합이 일어나기 어려울뿐만 아니라 그 자체의 열안정성도 만족스럽지 못한점에 착안하여 본 발명자들은 유기전기발광소자(OLED) 물질로서 열안정성이 우수하고 정공전달 특성과 발광특성이 우수한 신규물질을 사용함으로써 발광층에서의 정공,전자 재결합의 균형을 추구하여 안정성이 우수하면서도 높은 효율의 유기전기발광소자(OLED)를 제공하고자한다.TPD, which has been used mainly as a hole transport layer in previous technologies,

In view of the fact that NPD, etc., have insufficient hole transfer characteristics in terms of stability during device driving, effective hole and electron recombination is difficult to occur in the light emitting layer, and the thermal stability thereof is not satisfactory. As a light emitting device (OLED) material, an organic electroluminescent device (OLED) having high stability and high efficiency by pursuing a balance of hole and electron recombination in the light emitting layer by using a new material having excellent thermal stability, hole transporting characteristics and light emitting characteristics. Wish to provide).

In order to achieve the above object, the present invention provides a novel blue fluorescent substance of the general formula (I).

Wherein R _1, R ₂ , R ₃ is as defined above.

In addition, the present invention provides a method for preparing the compound of Formula (I) and an organic electroluminescent device comprising the compound in a hole transport layer and a light emitting layer.

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

The synthesis process of the novel blue fluorescent substance of the general formula (I) according to the present invention is represented by the following reaction scheme.

또는

or

Wherein R _1, R ₂ , R ₃ is as defined above.

The general formula (I) compound provided by the present invention has a glass transition temperature (Tg) of 140 ^° C. or higher, which significantly improves thermal stability as compared to conventional materials, and has good film characteristics. It is judged to be a compound with great applicability to electronic device materials. The specific example represented by general formula (I) is as follows. However, the present invention is not limited to the structure illustrated below.

Meanwhile, the methyl group-substituted nuxaphenylbenzene compound of formula (II), which is used as a starting material for synthesizing the present invention, was described by Muenen et al. In 1999. Chem., Int. Ed. Publications on pages 38, 3039 and 111, 3224, and 2004, Chem. Commun. Apply the same method as presented on page 336 and synthesize as follows.

The compound of formula (I) of the present invention exhibits excellent properties as a hole transport layer and a blue light emitting layer material of the organic electroluminescent device. When the compound of the present invention is used as the hole transport layer, the organic electroluminescent device is formed on an ITO glass substrate. After forming the hole injection layer using a conventionally used hole injection layer material such as 2-TNATA, the compound of formula (I) of the present invention is formed as a hole transport layer, and the light emitting layer and the electron transport layer are conventional methods. After laminating | stacking in order, it can obtain by laminating | stacking a metal electrode for cathodes. When the material of the present invention is used as a light emitting layer, a light blue light can be obtained by forming a layer of a compound of the general formula (I) in the light emitting layer in the same multilayer structure. Expression is possible.

The hole transport layer, the light emitting layer and the electron transport layer of the organic electroluminescent device may be deposited by wet coating or vacuum deposition such as spin coating, doctor blading, roll printing or screen printing, and the metal electrode may be coated by vacuum deposition. The material used to form the electron transport layer may be any known material, and examples of the metal electrode for the cathode may include magnesium, silver, calcium, aluminum, lithium, and alloys thereof.

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to the method presented in the Examples.

Preparation Example: Preparation of Methyl Substituted Hexaphenylbenzene Compound of Formula (II)

38.6 g (0.177 mol) of 4-iodotoluene was dissolved in 150 mL of triethylamine with 4.08 g (3.5 mmol) of Pd (PPh ₃ ) ₄ and 1.68 g (8.84 mmol) of CuI, and the mixture was stirred at room temperature for 5 minutes under nitrogen stream, followed by phenyl. Inject 18.1 g (0.177 mol) of acetylene for 30 minutes and stir at room temperature for 2 hours. After confirming that all reactions were removed by TLC, 300 mL of dichloromethane was added, stirred for 10 minutes, filtered, washed with methyl alcohol and acetone to obtain 4-toluylphenylacethylene as a pale yellow solid. (30.6 g, 90% yield)

8.57 g (44.6 mmol) of the compound obtained above and 17.16 g (44.6 mmol) of tetraphenylcyclopentadienone were added to 30 ml of phenyl ether and refluxed for 3 hours. After completion of the reaction by TLC, the reaction solution was cooled to 60 ^° C., 60 mL of THF was added and refluxed for 10 minutes. After cooling to room temperature, 300 mL of methyl alcohol was slowly added to solidify and filtered to obtain a compound of formula (II) as a pale yellow solid. (11.01 g, yield 45.0%)

Example 1

Step 1: 7.52 g (13.7 mmol) of the compound of formula (II), 2.93 g (16.46 mmol) of N-bromosuccinimide and 0.2 g of AIBN were added to 50 mL of carbon tetrachloride and heated under reflux for 10 hours. Stir. After confirming the completion of the reaction by TLC, the reaction mixture was cooled to room temperature, 50 mL of methanol was added to solidify and stirred for 5 minutes. Then filtered and washed with methanol and dried to give 4 ^, -bromomethylhexaphenylbenzene (7.82g, 91% yield).

Step 2: 2.0 g (3.19 mmol) of 4 ^, -bromomethylhexaphenylbenzene synthesized above was dissolved in 20 mL of triethyl phosphite and stirred under reflux for 20 hours under a nitrogen stream. After cooling to room temperature, 20 mL of nucleic acid was added to solidify, filtered and dried to obtain a nucleated phenyl benzene intermediate substituted with diethylphosphate as a white solid. (1.64 g, yield 75%)

Step 3: 0.3 g (0.44 mmol) of the above-described intermediate and 0.145 g (0.53 mmol) of 4-diphenylamino-benzaldehyde were added to 40 mL of dried THF, stirred for 2 hours under a nitrogen stream, and 0.3 g of NaH was added thereto. Stir at room temperature for 48 hours. 1 mL of water was added to the mixture, followed by removal of the solvent. After purification, the residue was purified by column chromatography to obtain a target compound having general formula (I) wherein R ₁ and R ₂ are phenyl and R ₃ is hydrogen. (0.12 g, yield 40%)

Example 2

Step 1 and Step 2 in Example 1 were carried out in the same manner, except that 0.079 g (0.53 mmol) of 4-dimethylaminobenzaldehyde was used instead of 4-diphenylaminobenzaldehyde in Step 3. In I), R ₁ and R ₂ are methyl groups and R ₃ is hydrogen. (0.13 g, 43% yield)

Example 3

 Step 1: The procedure is the same as in Step 1 of Example 1.

Step 2: 5.0 g (7.8 mmol) of 4 ^, -bromomethylhexaphenylbenzene ^and 2.47 g (9.4 mmol) of triphenylphosphine synthesized in Step 1 were added to 70 mL of DMF, and heated under nitrogen stream to reflux for 18 hours. After cooling to room temperature, 50 mL of ether was added, solidified, filtered, and recrystallized from dichloromethane and nucleic acid to obtain a white solid phosphonium bromide salt intermediate. (4.5g, 64% yield)

Step 3: 1.4 g (1.57 mmol) of the compound thus synthesized, 0.42 g (1.89 mmol) of 9-ethylcarbazole-3-carbaldehyde and 0.76 g (7.85 mmol) of t-BuONa were added to 30 mL of methanol and heated to reflux for 20 hours. Let's do it. After cooling to room temperature, 1.0 mmL of water was added to terminate the reaction. After removal of the solvent, the residue was purified by column chromatography to obtain a target compound of the general formula (I) in which R ₁ is an ethyl group and R ₂ is a phenyl group connected to R ₃ . 0.53 g, yield 45%)

Example 4 Fabrication of Organic Electroluminescent Device 1

-NPD를 사용하여 동일하게 제작한 유기전기발광소자와 특성을 비교하였다.Using the compound obtained in Example 1 as a hole transport layer material, an organic electroluminescent device was manufactured according to a conventional method and used as a conventional hole transport layer material.

The characteristics were compared with the organic electroluminescent device fabricated using -NPD.

First, a hole transport layer having a thickness of 50 nm was formed on the ITO layer formed on the glass substrate under a vacuum of 10 ^-6 Torr using a compound obtained in Example 1, and Alq3 was deposited at 300 kPa at a deposition rate of 0.3 kW / sec. It was deposited to a thickness to form a light emitting layer. An organic electroluminescent device was fabricated by depositing a thickness of 1500 kW at a rate of 10 kW / sec under a vacuum of 10 ^-6 Torr so that aluminum and lithium were 10 to 1 as cathode metals on the light emitting layer.

-NPD를 사용하여 50 nm 두께의 정공수송층을 형성시키고, 그 위에 발광층으로서 Alq3를 그리고 캐쏘드 금속으로 알루미늄과 리튬이 10대 1이 되도록 증착시켜 비교할 유기전기발광소자를 제작하였다In the same way, it has been used as a conventional hole transport material

A 50 nm-thick hole transport layer was formed using -NPD, and Alq3 was formed as a light emitting layer and aluminum and lithium were deposited to 10 to 1 by a cathode metal, thereby fabricating an organic electroluminescent device to be compared.

-NPD를 각각의 소자에서 정공 수송층으로 사용했을때의 인가전압과 전류밀도 특성곡선을 비교한 것을 도8에 나타내었다. 본 발명의 소자는 안정되게 발광을 하며 기존의 정공수송층 대비 더 우수한 특성의 소자를 구현할 수 있다.The structure of the device is shown in FIG. 1, and has been used as a compound synthesized in the present invention and a conventional hole transport layer material.

Fig. 8 shows a comparison of the applied voltage and current density characteristic curves when -NPD is used as the hole transport layer in each device. The device of the present invention can stably emit light and can implement a device having better characteristics than the existing hole transport layer.

Example 5 Fabrication of Organic Electroluminescent Device 2

Using the compounds obtained in Examples 1, 2, and 3 as the light emitting layer material, organic electroluminescent devices were manufactured according to a conventional method, and the device characteristics were compared.

-NPD를 사용하여 50 nm 두께의 정공수송층을 형성시키고, 그 위에 발광층으로서 실시예 1에서 얻은 화합물을 사용하여 0.3Å/초의 증착속도로 300Å의 두께로 증착시켜 발광층을 형성시켰다. 이 발광층위에 Alq3를 500Å의 두께로 증착시켜 전자주입 및 전달층을 형성시키고 그위에 캐쏘드 금속으로서 알루미늄과 리튬이 10대 1이 되도록 10^-6 토르의 진공하에 10Å/초 의 속도로 1500Å의 두께로 증착시켜 유기전기발광소자를 제작하였다.First, under a vacuum of 10 ^-6 Torr over an ITO layer formed on a glass substrate

A hole transport layer having a thickness of 50 nm was formed using -NPD, and the light emitting layer was formed by depositing 300 nm at a deposition rate of 0.3 mW / sec using the compound obtained in Example 1 as a light emitting layer thereon. Alq3 was deposited to a thickness of 500 kPa on the light emitting layer to form an electron injection and transport layer, and thereupon a thickness of 1500 kPa at a rate of 10 kV / sec under a vacuum of 10 ^-6 Torr to make aluminum and lithium 10 to 1 as a cathode metal. The organic electroluminescent device was manufactured by vapor deposition.

-NPD를 사용하여 50 nm 두께의 정공수송층을 형성시키고, 그 위에 발광층으로서 각각의 물질을 증착시키고, Alq3를 전자주입 및 전자전달층으로 그리고 캐쏘드 금속으로 알루미늄과 리튬이 10대 1이 되도록 증착시켜 비교할 유기전기발광소자를 제작하였다The materials obtained in Examples 2 and 3 have been used as the conventional hole transport layer materials in the same manner.

Form a 50 nm-thick hole transport layer using -NPD, deposit each material as a light-emitting layer, and deposit Alq3 as an electron injection and electron transport layer and a cathode metal with 10 to 1 aluminum and lithium The organic electroluminescent device to be compared was manufactured.

The luminous efficiency curve according to the current density of the devices thus manufactured is shown in FIG. 9.

The blue fluorescent dye for the organic electroluminescent device of the present invention is a useful material for producing an organic electroluminescent device having excellent stability as a hole transporting material, and when used as a light emitting layer, the emission color is expressed from blue to green region depending on the type of dopant to be used together. It is a useful light emitting material, and may be applied to the development of organic photoconductors, solar cells, etc., including organic electroluminescent devices.

Claims (3)

The novel blue fluorescent substance represented by the following general formula (I).

Wherein R ₁ and R ₂ are the same or different from each other and represent C1 to C4 alkyl, substituted or unsubstituted phenyl, naphthyl or anthracenyl groups, and R ₃ is linked to hydrogen or R ₂ to form a heterocyclic compound. The blue fluorescent substance according to claim 1, wherein the general formula (I) has a structure of any one of the following structural formulas.

An organic electroluminescent device using the blue fluorescent material according to claim 1 as a hole transport layer or a light emitting layer.

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