JP2000178548A - Luminescent material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an amorphous luminescent material which can be used in the form of a single thin film for a luminescent layer, can be used as a host material for other luminescent material, has excellent heat resistance and long-term stability, and does not readily crystalize by introducing various substituents into the benzanthracene ring. SOLUTION: This luminescent material includes compounds represented by formula I and formula II. In formula I, R1 to R10 are each H, alkyl or alkoxy; and R11 and R12 are each a phenyl, naphtyl, anthryl, phenanthryl, biphenyl or terphenyl group which may have a substituent selected from alkyl and alkoxy. In formula II, R1 to R10 are each H, alkyl or alkoxy; and R11 to R14 are each H, alkyl, alkoxy, or a phenyl, naphtyl or anthryl group which may have a substituent selected from alkyl and alkoxy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a luminescent material,
The present invention relates to an organic light emitting material applicable to a light emitting material of a display element typified by an organic thin film EL element and a fluorescent material excited by ultraviolet light.

[0002]

2. Description of the Related Art An organic thin-film EL device is a light-emitting device in which an organic material utilizing an electroluminescence (hereinafter referred to as EL) phenomenon is used as a light-emitting source, and is expected as a next-generation self-luminous flat display device or a flat light source. I have. The research on the organic EL device originated from a device using a single crystal of anthracene in the 1960's. After conducting research using various organic thin films, C.I. W. Tan
g, et al. report a revolutionary stacked device (Japanese Patent Laid-Open No. 59-1).
No. 94393, JP-A-63-264692,
JP-A-63-295695, Applied Physics Letter Vol. 51, No. 12, page 913 (1987)
), And Journal of Applied Physics, Vol. 65, No. 9, page 3610 (1989), etc.).

[0003] The C.I. W. The organic thin film EL device manufactured by Tang et al. Has a device structure in which an anode, an organic hole injection / transport layer, an organic light emitting layer, and a cathode are stacked on a transparent substrate. As a method for manufacturing an element, a transparent conductive film made of a composite oxide of indium and tin (hereinafter, referred to as ITO) is used as an anode on a transparent insulating substrate such as glass or a resin film by an evaporation method or a sputtering method. A single-layer film or a multilayer film of an organic hole injecting and transporting material represented by a copper phthalocyanine, a tetraaryldiamine compound and the like is formed thereon as an organic hole injecting and transporting layer.
It is formed by a vapor deposition method with a thickness of about nm or less. Next, an organic phosphor material such as tris (8-quinolinol) aluminum (hereinafter referred to as Alq) is used as an organic light emitting layer for 100 times.
It is formed by a vapor deposition method with a thickness of about nm or less. On this organic light emitting layer, aluminum: lithium (Al: Li),
An organic thin film EL element is manufactured by forming an alloy such as magnesium: silver (Mg: Ag) as a cathode having a thickness of about 200 nm by a co-evaporation method.

The organic thin film EL produced as described above
In the device, by applying a low DC voltage between the electrodes, positive charges (holes) are injected from the anode and negative charges (electrons) are injected into the organic light emitting layer from the cathode. The injected holes and electrons move in the organic thin film by the applied electric field, and recombine in the thin film with a certain probability. The energy released at this time excites the organic phosphor. The formed excitons emit light to the outside by the ratio of the emission quantum yield of the organic phosphor and return to the ground state. An element utilizing the fluorescence emitted from the exciton of the organic phosphor is an organic thin film EL element. The low DC voltage applied to this element is usually about 10 to 30 V, and the cathode is made of Mg: Ag.
An EL device using an alloy has a luminance of 10,000 cd / m ² or more.

[0005] However, the above-mentioned organic thin-film EL element has a problem in stability during continuous use, and it is necessary to improve emission luminance. As an attempt to improve the light emission luminance and stability of the device, there is a method of doping a light-emitting layer with a dye exhibiting strong fluorescence. In devices using quinacridone, which is a dye, as a guest substance, the efficiency and stability of the device have been improved (Japanese Patent Laid-Open No. 05-70).
773, JP-A-08-188772). However, this method has problems in that it is difficult to optimize the dopant concentration of the dye, so that doping is troublesome, and that it is difficult to uniformly disperse the dye in the light emitting layer.

As an attempt other than the doping method, there is a method in which a material which does not easily cause crystallization and has excellent thermal stability is used for the light emitting layer. In this method, the device can be easily manufactured as compared with the method of doping with a dye. In order to improve the stability of the device, a luminescent material having excellent thermal and temporal stability is required.

[0007]

As described above, in the organic thin-film EL device, the required characteristics such as the required brightness and the life of the device are not always satisfied. Currently, development of a highly durable and excellent luminescent material exhibiting high luminous efficiency is expected.

Since benzanthracene itself emits strong green fluorescence, it can be expected as a green light-emitting material. However, benzanthracene is easily crystallized due to its structure, and it is difficult to use it as a thin film for a display element as it is. For this reason, it is necessary to suppress crystallization by introducing a substituent having a large steric hindrance into the benzanthracene ring. By selecting the substituent to be introduced,
A benzanthracene derivative that emits strong green fluorescence with improved thermal stability and stability over time when formed into a thin film can be expected. By introducing a substituent, a film of the benzanthracene derivative alone can be used as a light emitting layer, and further, it can be expected as a host material of another light emitting material.

It is an object of the present invention to suppress crystallization by introducing various substituents into a benzanthracene ring, and it can be used as a single thin film in a light emitting layer, and can be used as a host material for other light emitting materials. An object of the present invention is to provide an amorphous light emitting material having excellent heat resistance and stability over time that can be used.

[0010]

SUMMARY OF THE INVENTION The present invention provides a derivative having a benzanthracene ring as a basic skeleton, and provides a luminescent material represented by the following general formula (1).

[0011]

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(Wherein, R _{1 to} R ₁₀ represent a hydrogen atom, an alkyl group, or an alkoxy group. R ₁₁ and R ₁₂ each represent a phenyl which may have a substituent selected from an alkyl group and an alkoxy group. Group, naphthyl group, anthryl group, phenanthryl group, biphenyl group and terphenyl group.)

The present invention provides a luminescent material represented by the following general formula (2) having a benzanthracene ring as a basic skeleton.

[0014]

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(Where R₁~ R_TenIs a hydrogen atom,
And an alkoxy group. R₁₁~ R ₁₄Is a hydrogen atom,
An alkyl group, an alkoxy group, or an alkyl group and
Or a substituent selected from alkoxy groups
Represents a phenyl group, a naphthyl group, and an anthryl group. )

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The luminescent material of the present invention is obtained by reacting benzanthraquinone with an aryl halide compound using an organolithium reagent, and subjecting this to an elimination reaction of a hydroxyl group. For example, it is synthesized by reacting benzanthraquinone with an aryl halide compound using butyllithium in a tetrahydrofuran solvent, and subjecting the obtained compound to dehydration cyclization using potassium iodide and sodium phosphinate under acidic conditions. be able to.

The light-emitting material of the present invention having a benzanthracene ring as a basic skeleton can emit green fluorescence because the benzanthracene ring itself emits green fluorescence.
It is also possible to change the emission color and increase the luminous efficiency by the substituent introduced. In addition, by introducing a substituent, thermal stability and temporal stability when used as a thin film can be improved.

The book represented by the above general formulas (1) and (2)
In the luminescent material of the invention, R₁~ R _TenStarts with a hydrogen atom
Methyl, ethyl, isopropyl, tertiary
-Butyl group, cyclohexyl group, trifluoromethyl group
Such as an alkyl group (where saturated cyclic hydrocarbon
Groups are also included in the alkyl groups), methoxy groups, ethoxy groups,
Representative of sopropoxy and tertiary butoxy groups
Specific examples such as an alkoxy group can be given. R₁
~ R_TenMay be the same or different.

In the luminescent material of the present invention represented by the above general formula (1), R _{11 to} R ₁₂ represent a naphthyl group which may have a substituent selected from an alkyl group and an alkoxy group;
Examples include an anthryl group, a phenanthryl group, a biphenyl group, and a terphenyl group.

In the luminescent material of the present invention represented by the above general formula (2), R _{11 to} R ₁₄ represent a phenyl group which may have a substituent selected from an alkyl group and an alkoxy group;
Examples include a naphthyl group, an anthryl group and a phenanthryl group.

Specific examples of the light emitting material represented by the general formulas (1) and (2) include the following compounds.

[0022]

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[0023]

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The light emitting material of the present invention described above can be used in combination with other charge transporting materials, light emitting materials and the like.

[0025]

Embodiments of the present invention will be described below. Example 1 4-bromotoluene in a nitrogen atmosphere
99 g was added to tetrahydrofuran, and while cooling, 25 ml of n-butyllithium (1.60 mol / l:
n-hexane solution) was added dropwise. After stirring for 1 hour after dropping, a tetrahydrofuran solution to which 2.58 g of 1,2-benzanthraquinone was added was dropped and stirred for 3 hours. After completion of the reaction, tetrahydrofuran was distilled off, pure water was added, and the organic layer was extracted with chloroform. The obtained product was purified by column treatment using toluene / acetone. Next, acetic acid was added to 2.20 g of the purified compound, and 2.08 g of potassium iodide and 0.66 g of sodium phosphinate were sequentially added thereto, followed by stirring and reflux for 1 hour. The obtained product was purified by recrystallization using toluene / hexane to obtain a benzanthracene derivative in the form of a yellowish white powder represented by the following chemical formula (7).

[0026]

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The benzanthracene derivative (Chemical Formula 7) obtained as described above was subjected to mass spectrometry (using JMN SX102 manufactured by JEOL Ltd.) to obtain an m / z 408 corresponding to the molecular ion of the target compound. Since the ion peak was detected, the benzanthracene derivative (Chem. 7)
Generation was confirmed. FIG. 1 shows the NMR spectrum of the benzanthracene derivative (Chemical Formula 7) (JMN-LA40 manufactured by JEOL Ltd.).
0 is used).

The glass transition point (Tg) of this benzanthracene derivative (Chem. 7) was measured under a nitrogen atmosphere at a heating rate of 10 ° C./min (using DSC220C manufactured by Seiko Instruments Inc.). Transition point is 8
It was found to be 5 ° C. This benzanthracene derivative (Chemical Formula 7) does not show a crystallization peak, so that an amorphous thin film exhibiting high temporal stability can be expected.

As a result of forming a vapor-deposited film made of this benzanthracene derivative (Formula 7) on quartz glass and measuring the ionization potential using a surface analyzer (using AC-1 manufactured by Riken Keiki Co., Ltd.), It was found to be 5.56 eV.

Using the same thin film as described above, the fluorescence (PL) spectrum of the benzanthracene derivative (Formula 7) was measured (using RF5000 manufactured by Shimadzu Corporation). As a result, the benzanthracene derivative (Formula 7) was , 452
And a material emitting blue fluorescence having a peak at 482 nm.

(Example 2) In a nitrogen atmosphere, 8.28 g of 1-bromonaphthalene was added to tetrahydrofuran, and 29 ml of n-butyllithium was added dropwise while cooling the mixture. After stirring for 1 hour after the addition, a tetrahydrofuran solution to which 3.87 g of 1,2-benzanthraquinone was added was added dropwise, followed by stirring for 2 hours. After completion of the reaction, tetrahydrofuran was distilled off, pure water was added, and the organic layer was extracted with chloroform. The product obtained is chloroform /
Purified by recrystallization using hexane. Acetic acid was added to 3.10 g of the purified compound, and then potassium iodide (2.50) was added.
g and 0.80 g of sodium phosphinate were added, and the mixture was stirred and refluxed for 1 hour. The obtained product was purified by recrystallization using toluene to obtain a benzanthracene derivative in the form of a yellow powder represented by the following chemical formula (8).

[0032]

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The benzanthracene derivative (Chemical Formula 8) obtained as described above was subjected to mass spectrometry, and an ion peak at m / z 480 corresponding to the molecular ion of the target compound was detected. Generation 8) was confirmed. FIG. 2 shows the NMR spectrum of the benzanthracene derivative (Chemical Formula 8) (JMN-LA manufactured by JEOL Ltd.).
400 is used).

This benzanthracene derivative (Formula 8)
The glass transition point (Tg) was measured under a nitrogen atmosphere under a condition of a temperature rise rate of 10 ° C./min. As a result, it was found to be 139 ° C. As a result of comparison with the above-mentioned benzanthracene derivative (Formula 7), it was confirmed that Tg greatly changed depending on the substituent to be introduced. This benzanthracene derivative (Chemical Formula 8) did not show a crystallization peak, so that an amorphous thin film showing high temporal stability can be expected.

A vapor-deposited film made of the benzanthracene derivative (Formula 8) was formed on quartz glass, and the ionization potential was measured using a surface analyzer.
eV.

Using the same thin film as described above, the fluorescence (PL) spectrum of the benzanthracene derivative (formula 8) was measured.
It was found that the material emitted green fluorescence having a peak at 7,542 nm.

Example 3 In a nitrogen atmosphere, 7.71 g of 9-bromoanthracene was added to tetrahydrofuran.
While cooling this, 21 ml of n-butyllithium was added dropwise. After stirring for 1 hour after the addition, a tetrahydrofuran solution to which 2.58 g of 1,2-benzanthraquinone was added was added dropwise and the mixture was stirred for 2 hours. After completion of the reaction, tetrahydrofuran was distilled off, pure water was added, and the organic layer was extracted with chloroform. The product obtained is chloroform /
It was purified by recrystallization using hexane. Purified compound
Acetic acid was added to 96 g, then 2.00 g of potassium iodide,
0.64 g of sodium phosphinate was added, and the mixture was stirred and refluxed for 1 hour. The obtained product was purified by recrystallization using toluene / hexane to obtain a benzanthracene derivative in the form of a yellow powder represented by the following chemical formula (9).

[0038]

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The benzanthracene derivative (Chemical Formula 9) obtained as described above was subjected to mass spectrometry, and an ion peak at m / z 580 corresponding to the molecular ion of the target compound was detected. Generation 9) was confirmed. FIG. 3 shows an IR spectrum of a benzanthracene derivative (Chem. 9) (F by Shimadzu Corporation).
TIR-8100M, KBr tablet method).

The glass transition point (Tg) of this benzanthracene derivative (Formula 9) was measured under a nitrogen atmosphere at a rate of temperature increase of 10 ° C./min, and was found to be 187 ° C.

A vapor-deposited film composed of the benzanthracene derivative (Formula 9) was formed on quartz glass, and the ionization potential was measured using a surface analyzer.
eV.

Using the same thin film as described above, the fluorescence (PL) spectrum of the benzanthracene derivative (Chemical Formula 9) was measured.
The material was found to emit green fluorescence having a peak at 08 and 545 nm.

Example 4 In a nitrogen atmosphere, 8.33 ml of 2-bromobiphenyl was added to tetrahydrofuran.
36 ml of n-butyllithium was added dropwise thereto. After stirring for 1 hour after the dropwise addition, 1,2-benzanthraquinone 5.
17 g of tetrahydrofuran solution was added dropwise and stirred for 2 hours. After completion of the reaction, tetrahydrofuran was distilled off and extracted with chloroform. The obtained product was purified by recrystallization using toluene / hexane. Acetic acid was added to 2.00 g of the purified compound, then 1.45 g of potassium iodide and 0.46 g of sodium phosphinate were added, and the mixture was stirred and refluxed for 1 hour. The obtained product was purified by recrystallization using toluene / hexane to obtain a benzanthracene derivative in the form of a yellow powder represented by the following chemical formula (10).

[0044]

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The benzanthracene derivative (Chemical Formula 10) obtained as described above was subjected to mass spectrometry, and an ion peak at m / z 532 corresponding to the molecular ion of the target compound was detected. The formation of Chemical formula 10) was confirmed. FIG. 4 shows the NMR spectrum of the benzanthracene derivative (Chemical Formula 10).

This benzanthracene derivative (formula 10)
The glass transition point (Tg) of the sample was measured under a nitrogen atmosphere at a rate of temperature rise of 10 ° C./min. As a result, it was found to be 86 ° C. Since the benzanthracene derivative (Chemical Formula 10) did not show a crystallization peak, an amorphous thin film showing high temporal stability can be expected.

This benzanthracene derivative (formula 10)
Was formed on quartz glass, and the ionization potential was measured using a surface analyzer.
It was found to be 3 eV.

Using the same thin film as described above, the fluorescence (PL) spectrum of the benzanthracene derivative (Formula 10) was measured.
Was found to be a material that emits green fluorescence having a peak at 509 and 547 nm.

The luminescent material having a benzanthracene ring as a basic skeleton in the above examples can change the luminescent color, glass transition point and crystallinity by introducing a substituent, and is excellent in thermal stability and It is possible to obtain a thin film having good temporal stability which is difficult to be formed.

[0050]

As described above, when a material having a benzanthracene ring as a basic skeleton into which various substituents are introduced according to the present invention is used, the amorphous material having high heat resistance and high aging stability is hardly crystallized. Can be obtained. Accordingly, by forming a light-emitting site using a material having a basic skeleton of a benzanthracene ring having high heat resistance and high aging stability and having high stability according to the present invention, a light-emitting element having high heat stability and high durability can be obtained. Can be expected.

[0051]

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an NMR spectrum of a light emitting material according to Example 1 of the present invention.

FIG. 2 is an explanatory diagram showing an NMR spectrum of a light emitting material according to Example 2 of the present invention.

FIG. 3 is an explanatory diagram showing an IR spectrum of a light emitting material according to Example 3 of the present invention.

FIG. 4 is an explanatory diagram showing an NMR spectrum of a light emitting material according to Example 4 of the present invention.

Claims (2)

[Claims] (1) a benzanthracene ring having a basic skeleton;
A light-emitting material represented by the following general formula (1). Embedded image (Wherein, R _{1 to} R ₁₀ represent a hydrogen atom, an alkyl group, or an alkoxy group. R ₁₁ and R ₁₂ represent a phenyl group, a naphthyl group which may have a substituent selected from an alkyl group and an alkoxy group) Group, anthryl group, phenanthryl group, biphenyl group and terphenyl group.) 2. A benzanthracene ring having a basic skeleton,
A luminescent material represented by the following general formula (2)
Fees. Embedded image(Where R₁~ R_TenRepresents a hydrogen atom, an alkyl group, an alcohol
Shows a xy group. R₁₁~ R ₁₄Is a hydrogen atom, an alkyl group,
Alkoxy group, or alkyl group and alkoxy
A phenyl group which may have a substituent selected from a group,
Represents a naphthyl group or an anthryl group. )