JPH11323323A - Luminescent material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide amorphous blue luminescent materials with excellent heat-resistance and aging stability obtained by reacting anthraquinone derivatives with halogenated aryl compounds, and thereafter subjecting the resultant to cyclodehydration. SOLUTION: Luminescent materials having anthracene rings as the base backbone, represented by the formula (wherein R1 -R8 are each H, alkyl or alkoxy, and R9 -R10 are each naphthyl, anthryl, phenanthryl, biphenyl or terphenyl which may have a substituting group selected from alkyl and alkoxy) are obtained by reacting anthraquinone derivatives with halogenated aryl compounds in a diethyl ether solvent in the presence of butylithium, and subjecting the resulting compounds to cyclodehydration under acid conditions using potassium iodide and sodium phosphinate. Thus, amorphous luminescent elements with hardly crystallizing property and excellent in heat-stability and durability can be obtained.

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 type flat display device or a flat light source. I have. This organic EL
The research of the device originated from a device using a single crystal of anthracene in the 1960s, and after conducting research using a variety of organic thin films, C.I. W. Ta
ng et al. report a revolutionary stacked device (Japanese Patent Laid-Open No.
194393, JP-A-63-264692, JP-A-63-295695, Applied Physics Letter Vol. 51, No. 12, page 913 (19)
1987), and Journal of Applied Physics, Vol. 65, No. 9, page 3610 (1989), etc.), and active research and development activities have been developed.

[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.

However, most of the luminescent materials used in the above-mentioned organic thin-film EL devices emit green or yellow light, and there are reports on EL devices using blue and red luminescent materials required for full-color display. limited.

A blue light emitting EL device using an organic material is disclosed in Begins with devices using anthracene crystals by Helfrich et al. (Physical Review Letter No. 14
Vol. 229 (1965)), and recently, a device using tetraphenylbutadiene as a light emitting material and exhibiting a luminance of 100 cd / m ² or more (Japanese Patent Laid-Open No. 59-194393).
And a device using a distyrylbenzene derivative as a light-emitting material and emitting blue-green light with a luminance of 800 cd / m ² or more has been reported (Japanese Patent Publication No. 7-119407). In addition, a device using an acridone-based compound as a light-emitting material has been reported to emit blue light of 2500 cd / m ² or more (JP-A-8-67873).

[0007] Such blue light-emitting materials have fewer reports than green or yellow light-emitting materials, and it can be said that research and development of the materials are delayed.

[0008]

As described above, there have been few reports on materials that have been used as blue light-emitting materials in organic thin-film EL devices, and they do not always satisfy the required characteristics. Currently, development of a highly durable luminescent material having excellent blue luminous efficiency is expected.

Anthracene itself can be expected as a blue light emitting material because it emits blue fluorescence. But,
Anthracene is easily crystallized, and it is difficult to use it as a thin film for a display element. For this reason, it is necessary to suppress the crystallization by introducing a substituent into the anthracene ring. By selecting a substituent to be introduced, an anthracene derivative that emits blue fluorescence with improved thermal stability and stability over time when formed into a thin film can be expected. Further, by introducing a substituent having a charge transporting property, a light emitting material having a charge transporting property or a charge transporting material can be expected. By introducing a substituent, a film of an anthracene derivative alone can be used as a light emitting layer, and further, it can be expected as a host material of another blue light emitting material.

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

[0011]

The present invention provides a derivative having an anthracene ring as a basic skeleton and a luminescent material represented by the following general formula (1).

[0012]

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(Wherein, R _{1 to} R ₈ represent a hydrogen atom, an alkyl group, or an alkoxy group. R ₉ and R ₁₀ represent a naphthyl which may have a substituent selected from an alkyl group and an alkoxy group. 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 an anthracene ring as a basic skeleton.

[0015]

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(Wherein R₁~ R₈Is a hydrogen atom,
And an alkoxy group. R₉~ R ₁₂Is an alkyl group
And has a substituent selected from an alkoxy group
Good phenyl, naphthyl, anthryl, phenane
Represents a tolyl group, a biphenyl group, or a terphenyl group. )

The present invention provides a light-emitting material having an anthracene ring as a basic skeleton, which is represented by the following general formula (3).

[0018]

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(Wherein, R _{1 to} R ₈ represent a hydrogen atom, an alkyl group, or an alkoxy group. R ₉ represents an oxazole ring,
It represents a heterocyclic compound represented by an oxadiazole ring and a thiophene ring. R ₁₀ represents a phenyl group, a naphthyl group, or a biphenyl group which may have a substituent selected from an alkyl group and an alkoxy group. )

The present invention provides a light emitting material having an anthracene ring represented by the general formula (3) as a basic skeleton, wherein the light emitting material is represented by the following general formula (4).

[0021]

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(Wherein, R _{1 to} R ₈ represent a hydrogen atom, an alkyl group, or an alkoxy group. R ₉ and R ₁₀ each represent a phenyl which may have a substituent selected from an alkyl group and an alkoxy group. Group, naphthyl group and biphenyl group.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION The blue light-emitting material of the present invention is obtained by reacting an anthraquinone derivative with an aryl halide compound and subjecting this to dehydration cyclization. For example, it is synthesized by reacting an anthraquinone derivative with an aryl halide compound using butyllithium in a diethyl ether solvent, and subjecting the obtained compound to dehydration cyclization using potassium iodide and sodium phosphinate under acidic conditions. be able to.

The blue light-emitting material of the present invention having an anthracene ring as a basic skeleton can be expected to emit blue fluorescence because the anthracene ring itself emits blue fluorescence, and the luminous efficiency can be increased by the substituent introduced. . In addition, by introducing a substituent, thermal stability and temporal stability when used as a thin film can be improved. Furthermore,
By introducing a substituent having a charge transporting property, it is also possible to obtain a material which simultaneously functions as a charge transporting material.

In the blue light-emitting material of the present invention represented by the above general formulas (1) to (4), R _{1 to} R ₈ include a hydrogen atom, a methyl group, an ethyl group, an isopropyl group, a tertiary butyl group, a cyclohexyl group. Group, an alkyl group represented by a trifluoromethyl group and the like (here, a saturated cyclic hydrocarbon group is also included in the alkyl group), a methoxy group, an ethoxy group,
Specific examples include an alkoxy group represented by an isopropoxy group and a tertiary butoxy group. R
_{1 to} R ₈ may be the same or different.

In the blue light-emitting material of the present invention represented by the above general formula (1), R _{9 to} R ₁₀ represent a naphthyl group, an anthryl group, which may have a substituent selected from an alkyl group and an alkoxy group, Phenanthryl group, biphenyl group,
And terphenyl groups.

In the blue light-emitting material of the present invention represented by the general formula (2), R _{9 to} R ₁₂ represent a phenyl group, 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 blue light emitting material of the present invention represented by the general formula (3), R ₉ represents a heterocyclic compound containing at least one hetero atom. Representative examples of the heterocyclic compound include a thiophene ring, an oxazole ring, and an oxadiazole ring. Examples of R ₁₀ include a phenyl group, a naphthyl group, and a biphenyl group which may have a substituent selected from an alkyl group and an alkoxy group.

In the blue light-emitting material of the present invention represented by the general formula (4), R _{9 to} R ₁₀ represent a phenyl group, a naphthyl group, which may have a substituent selected from an alkyl group and an alkoxy group, Shows a biphenyl group. General formula (1),
Specific examples of the light emitting material represented by (2), (3) and (4) include the following.

[0030]

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[0031]

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[0032]

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The blue light-emitting material of the present invention described above can be used as a mixture with other charge transporting materials, light-emitting materials and the like.

[0034]

Embodiments of the present invention will be described below. (Example 1) In a nitrogen atmosphere, 8.16 g of 2-bromobiphenyl was added to diethyl ether, and 25 ml of n-butyllithium (1.60 mol /
l) was added dropwise. After stirring for 1 hour after dropping, a diethyl ether solution to which 3.20 g of 2-tert-butylanthraquinone was added was dropped and stirred for 2 hours. After the completion of the reaction, pure water was added to the reaction solution, and the product obtained by extracting the organic layer was purified by recrystallization using toluene as a good solvent and hexane as a poor solvent. Next, acetic acid was added to the purified compound, potassium iodide and sodium phosphinate were sequentially added thereto, and the mixture was refluxed for 1 hour. The obtained product was recrystallized using toluene / hexane and purified to obtain a white powdery anthracene derivative represented by the following chemical formula.

[0035]

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Mass spectrometry of the anthracene derivative obtained as described above (JMNS manufactured by JEOL Ltd.)
X102), and an ion peak at m / z 538 corresponding to the molecular ion of the target compound was detected. Thus, formation of the anthracene derivative (Formula 7) was confirmed. FIG. 1 shows the IR spectrum of an anthracene derivative (using FTIR-8100M manufactured by Shimadzu Corporation, KBr tablet method).

The glass transition point (Tg) of this anthracene derivative was found to be 74 ° C. by using a DSC 220C manufactured by Seiko Denshi Kogyo KK under a nitrogen atmosphere at a temperature rising rate of 10 ° C./min. Do you get it. Since the anthracene derivative (Formula 7) did not show a crystallization peak, an amorphous thin film having high temporal stability can be expected. A vapor deposition film made of this anthracene derivative was formed on quartz glass, and the ionization potential was measured using a surface analyzer (using AC-1 manufactured by Riken Keiki Co., Ltd.). As a result, it was found to be 5.97 eV. Was.

The fluorescence (PL) spectrum of the anthracene derivative was measured using a thin film similar to the above (using RF5000 manufactured by Shimadzu Corporation). As a result, the anthracene derivative showed a blue color having peaks at 423 and 444 nm. It was confirmed that the material emitted fluorescence.

Example 2 In a nitrogen atmosphere, 10.3 g of 9-bromophenanthrene was added to diethyl ether.
While cooling this, 28 ml of n-butyllithium was added dropwise. After stirring for 1 hour after the addition, a diethyl ether solution to which 4.00 g of 2-tert-butylanthraquinone was added was added dropwise, and the mixture was stirred for 2 hours. After the completion of the reaction, pure water was added to the reaction solution, and the product obtained by extracting the organic layer was purified by recrystallization using toluene and hexane as a poor solvent.

Acetic acid was added to the purified compound, and then potassium iodide and sodium phosphinate were added, and the mixture was stirred and refluxed for 1 hour. The resulting product was purified by recrystallization using toluene to obtain a white powdery anthracene derivative represented by the following chemical formula.

[0041]

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The anthracene derivative obtained as described above was subjected to mass spectrometry, and an ion peak at m / z 586 corresponding to the molecular ion of the target compound was detected. Thus, formation of the anthracene derivative was confirmed. FIG. 2 shows an IR spectrum (KBr tablet method) of the anthracene derivative.

The glass transition point (Tg) of this anthracene derivative was determined to be 190 ° C. in a nitrogen atmosphere at a temperature rising rate of 10 ° C./min. As a result of comparison with the anthracene derivative of Example 1, it was confirmed that Tg greatly changed depending on the substituent to be introduced.

A vapor deposition film made of this anthracene derivative was formed on quartz glass, and the ionization potential was measured using a surface analyzer. As a result, it was found to be 5.90 eV.

As a result of measuring the fluorescence (PL) spectrum of the anthracene derivative using the same thin film as described above, it was found that this anthracene derivative is a material emitting blue fluorescence having a peak at 443 nm.

Example 3 7.53 g of 5'-bromo-1,1 ': 3', 1 "-terphenyl was added to diethyl ether in a nitrogen atmosphere, and n-butyllithium was added thereto while cooling with ice. After stirring for 1 hour after dropping, 2.11 g of 2-tert-butylanthraquinone was added.
Was added dropwise, and the mixture was stirred for 2 hours. After completion of the reaction, pure water was added to the reaction solution, and the product obtained by extracting the organic layer was purified by recrystallization using toluene as a good solvent and hexane as a poor solvent.

Acetic acid was added to the purified compound, and then potassium iodide and sodium phosphinate were added, and the mixture was stirred and refluxed for 1 hour. The obtained product was recrystallized using toluene / hexane and purified to obtain a white powdery anthracene derivative represented by the following chemical formula.

[0048]

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The anthracene derivative obtained as described above was subjected to mass spectrometry, and an ion peak at m / z 690 corresponding to the molecular ion of the target compound was detected. Thus, formation of the anthracene derivative was confirmed. FIG. 3 shows an NMR spectrum of the anthracene derivative (Formula 9).

The glass transition point (Tg) of this anthracene derivative was measured at a rate of 10 ° C./min in a nitrogen atmosphere, and it was found to be 130 ° C. Since the anthracene derivative did not show a crystallization peak, an amorphous thin film exhibiting high temporal stability can be expected.

A vapor deposition film made of this anthracene derivative was formed on quartz glass, and the ionization potential was measured using a surface analyzer. As a result, it was found to be 5.83 eV.

The fluorescence (PL) spectrum of the anthracene derivative was measured using the same thin film as described above. As a result, the anthracene derivative was found to be a material emitting blue fluorescence having a peak at 453 nm.

Example 4 In a nitrogen atmosphere, 2- (3-
Bromophenyl) -5- (2-naphthyl) -1,3,4
9.83 g of -oxadiazole was added to THF, and 22 ml of n-butyllithium was added dropwise thereto. After stirring for 1 hour after dropping, 2.65 g of 2-tert-butylanthraquinone was dropped and stirred for 2 hours. The obtained product was purified by recrystallization using toluene as a good solvent and hexane as a poor solvent.

Acetic acid was added to the purified compound, and then potassium iodide and sodium phosphinate were added, and the mixture was stirred and refluxed for 1 hour. The obtained product was recrystallized using toluene / hexane and purified to obtain a white powdery anthracene derivative represented by the following chemical formula.

[0055]

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The anthracene derivative obtained as described above was subjected to mass spectrometry, and an ion peak at m / z 774 corresponding to the molecular ion of the target compound was detected. Thus, formation of the anthracene derivative was confirmed. FIG. 4 shows an NMR spectrum of the anthracene derivative.

The glass transition point (Tg) of this anthracene derivative was measured under a nitrogen atmosphere at a heating rate of 10 ° C./min. As a result, it was found to be 147 ° C. Since the anthracene derivative did not show a crystallization peak, an amorphous thin film exhibiting high temporal stability can be expected.

A vapor deposition film made of this anthracene derivative was formed on quartz glass, and the ionization potential was measured using a surface analyzer to find that it was 5.88 eV.

The fluorescence (PL) spectrum of the anthracene derivative was measured using the same thin film as described above. As a result, this anthracene derivative was found to be a material emitting blue fluorescence having a peak at 445 nm.

The blue light-emitting material having an anthracene ring as a basic skeleton in the above examples can change the glass transition point and the crystallinity by introducing a substituent, is excellent in thermal stability, and is hardly crystallized over time. A thin film having good stability can be obtained.

[0061]

As described above, according to the present invention, by forming a light-emitting site using a material having an anthracene ring as a basic skeleton into which various substituents have been introduced, high heat resistance and high temporal stability can be obtained. It is possible to obtain an amorphous thin film that is difficult to crystallize. Thereby, a light emitting element having high thermal stability and high durability can be expected.

[0062]

[Brief description of the drawings]

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

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

FIG. 3 is an explanatory diagram showing an NMR 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 (4)

[Claims] 1. A light-emitting material represented by the following general formula (1) having an anthracene ring as a basic skeleton. Embedded image (Wherein, R _{1 to} R ₈ represent a hydrogen atom, an alkyl group, or an alkoxy group. R ₉ and R ₁₀ represent a naphthyl group which may have a substituent selected from an alkyl group and an alkoxy group, an anthryl Group, phenanthryl group, biphenyl group, terphenyl group.) 2. The following one having an anthracene ring as a basic skeleton.
A light-emitting material represented by the general formula (2). Embedded image(Where R₁~ R₈Represents a hydrogen atom, an alkyl group, an alcohol
Shows a xy group. R₉~ R ₁₂Represents an alkyl group and an alcohol
Phenyl optionally having a substituent selected from xy groups
Group, naphthyl group, anthryl group, phenanthryl group,
Represents phenyl and terphenyl groups. ) 3. A light-emitting material represented by the following general formula (3) having an anthracene ring as a basic skeleton. Embedded image (Wherein, R ₁ to R ₈ are, .R ₉ showing the hydrogen atom, an alkyl group, an alkoxy group, .R ₁₀ representing the oxazole ring, oxadiazole ring, heterocyclic compounds typified by thiophene ring, Represents a phenyl group, a naphthyl group, or a biphenyl group which may have a substituent selected from an alkyl group and an alkoxy group.) 4. A light emitting material having an anthracene ring as a basic skeleton according to claim (3), characterized by being represented by the following general formula (4). Embedded image (Wherein, R _{1 to} R ₈ represent a hydrogen atom, an alkyl group, or an alkoxy group. R ₉ and R ₁₀ represent a phenyl group, a naphthyl which may have a substituent selected from an alkyl group and an alkoxy group) A biphenyl group.)