JP2002284718A - Polyarylene compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyarylene compound of amorphous type, capable of stably developing pure blue luminescence, capable of exhibiting a clear glass- transition point so as to be scarcely crystallized, and capable of being subjected to vacuum deposition. SOLUTION: This polyarylene compound is expressed by the general formula (1) [R<1> , R<2> , R<3> , R<4> , R<5> , RS<6> , R<7> , R<8> , RS<9> , R<10> , R<11> , and R<12> may be each an alkyl having carbon number of not more than 10; at least one of the benzene rings in the general formula (1) is condensed with at least one of other benzene rings; and n<1> , n<2> , n<3> , n<4> , n<5> , n<6> , n<7> , and n<8> are ach an integer of 0 to 5]. The polyarylene compound has a glass-transition point clearer than those of conventional compounds by selecting its substituents so as to have suitable heat stability for vacuum deposition. Further the polyarylene compound develops the stable blue luminescence so as to be excellent in availability as a luminescent material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyarylene compound useful as a light emitting material of an organic electroluminescent device.

[0002]

2. Description of the Related Art Organic electroluminescent elements (EL elements) and the like have recently attracted attention as one candidate for flat panel displays that are self-luminous, have a high response speed, and have no viewing angle dependence. There is an increasing interest in organic light emitting materials as constituent materials. The first advantage of organic light emitting materials is that
The molecular design allows the optical properties of the material to be controlled to some extent, which makes it possible to realize a full-color organic light-emitting device in which all of the three primary colors of red, blue, and green are manufactured using the respective light-emitting materials.

[0003] For example, polyarylene compounds are known as organic light-emitting materials, and among them, para-sexiphenyl derivatives are used as materials suitable for light emission in the blue light-emitting region. This sexiphenyl derivative or its analogous compound was not necessarily a suitable compound as an organic EL material because of its low solubility in organic solvents and its high crystallinity. However,
Presentation by F. Maghdeli et al. Using sexiphenyl [Synthe
tic Metals (1997), 85. 1441-1442], and the use value of polyarylene compounds has been increasing.

[0004] In particular, Spiro 6φ of the following structural formula (3) in which sexiphenyl is bonded with spiro quaternary carbon from Hoechst has a high glass transition temperature (Tg) and is an organic EL device prepared by spin coating. without inter alia long crystallization, it has been reported to exhibit blue light emission (see Japanese Patent Laid-Open No. 7-278537).

[0005]

Embedded image Structural formula (3):

[0006]

However, in Japanese Patent Application Laid-Open No. 7-278538, there is no description of emission chromaticity, and the spectrum (J.Salback (Hoechst) of an organic electroluminescent device using the spiro compound is not disclosed. Synthetic M
etals (1997), 91, 209-215) cannot be said to have reached the chromaticity region considered to be pure blue.

Further, in order to further increase the utility value of the compound, it is required that the device not be crystallized for a long time not only in the spin coating method but also in the device formed by the vacuum evaporation method. For this purpose, it is desired to develop a material that satisfies the requirement for reducing crystallization of spiro-6φ and that can be vacuum-deposited at a low temperature.

[0008] The present inventor first uses a unique profile,
A heat measurement of Spiro-6φ was performed. As a result, the following three points were obtained as measurement results. That is, (1) no clear glass transition temperature was observed (2) the crystallization point was 347
° C. (3) The melting point was 385 ° C. Therefore, the search for a material compound exhibiting a clear glass transition temperature with this unique profile has become an issue.

An object of the present invention is to provide an amorphous polyarylene compound which exhibits a stable blue light emission, exhibits a clear glass transition temperature, is hardly crystallized, and can be vacuum-deposited.

[0010]

That is, the present invention relates to a polyarylene compound represented by the following general formula (1).

Embedded image General formula (1): (However, in the general formula (1), R ¹ , R ² , R ³ ,
R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ and R
¹² is each independently a methyl group having 10 or less carbon atoms,
It may be an alkyl group such as an ethyl group and a propyl group. Further, at least one of the benzene rings in the general formula (1)
In particular, the benzene ring having R ² , R ⁵ , R ⁸ , and R ¹¹ is condensed with at least one benzene ring to form a naphthalene ring or the like, and n ¹ , n ² , n ³ , and n ⁴ , N ⁵ , n ⁶ , n ⁷
And n ⁸ are each independently an integer from 0 to 5. )

According to the present invention, the polyarylene compound represented by the general formula (1) exhibits a clearer glass transition temperature than conventional materials due to the selection of the substituent, and has a thermal stability suitable for vacuum deposition. have.

The polyarylene compound exhibits stable blue light emission and is excellent in use value as a luminescent material.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described more specifically based on embodiments.

Examples of the polyphenylene compound include those represented by the following general formula (2), and those specifically represented by the following structural formulas (1) and (2).

Embedded image General formula (2):

Embedded image Structural formula (1):

[Image Omitted] Structural formula (2):

FIGS. 6 to 9 show examples of an organic electroluminescent device (EL device) using a polyarylene compound according to the present invention as an organic luminescent material.

FIG. 6 shows a transmissive organic electroluminescent device A in which emitted light 20 is transmitted through the cathode 3.
Observable from the side. FIG. 7 shows a reflective organic electroluminescent device B in which reflected light from the cathode 3 is also obtained as emitted light 20.

In FIG. 1, reference numeral 1 denotes a substrate for forming an organic electroluminescent element, which may be made of glass, plastic or other appropriate material. In addition, when the organic electroluminescent element is used in combination with another display element, the substrate can be shared. For example, in the case of active matrix driving, a TFT (Thin Film Transistors) can be used as the substrate. It is possible.
Reference numeral 2 denotes a transparent electrode (anode). For example, in the above-mentioned transmission type organic electroluminescent device A, a transparent electrode ITO (Indium tin oxidizer) is used.
e), IZO (Indium zinc oxide), SnO _{2 and the} like can be used. In the reflection type organic electroluminescent device B, Cr, Fe,
Co, Ni, Cu, Ta, W, Pt, Mo, Au and alloys thereof can be used.

Reference numeral 5 denotes an organic light emitting layer, which contains a polyarylene compound according to the present invention as a light emitting material. With respect to this light-emitting layer, conventionally known various structures can be used as a layer structure for obtaining the organic electroluminescence 20. As will be described later, for example, when a material constituting either the hole transport layer or the electron transport layer has a light emitting property, a structure in which these thin films are laminated can be used. In order to further enhance the charge transport performance, one or both of the hole transport layer and the electron transport layer has a structure in which thin films of a plurality of types of materials are stacked,
Alternatively, use of a thin film having a composition in which a plurality of types of materials are mixed is not prevented. Further, in order to enhance the luminous efficiency,
Using at least one or more kinds of fluorescent material, the sandwich structure between the thin hole transport layer and an electron transporting layer, further a hole transporting layer at least one kind of fluorescent material or the electron transport layer Alternatively, a structure included in both of them may be used. In these cases, a thin film for controlling the transport of holes or electrons can be included in the layer structure in order to improve the luminous efficiency.

The polyarylene compound according to the present invention comprises
Since it has both electron transporting performance and hole transporting performance, it can be used as a light emitting layer also serving as an electron transporting layer or as a light emitting layer also serving as a hole transporting layer in the device configuration. In addition, it is also possible to adopt a configuration in which the polyarylene compound according to the present invention is used as a light emitting layer and is sandwiched between an electron transport layer and a hole transport layer.

In FIGS. 6 and 7, reference numeral 3 denotes a cathode;
Examples of the electrode material include an alloy of an active metal such as Li, Mg, and Ca and a metal such as Ag, Al, and In, LiF, and Li.
O ₂ or a structure in which these are laminated can be used. In a transmission type organic electroluminescent device, by adjusting the thickness of the cathode, a light transmittance suitable for the intended use can be obtained. On the other hand, in the reflection type organic electroluminescent device, the cathode is made thin to maintain high transmittance, and the anode is made of a material having high reflectance, so that the organic electroluminescence can be taken out to the cathode side. Can be. Further, reference numeral 4 in the drawing denotes a sealing / protecting layer, and its effect is improved by adopting a structure that covers the entire organic electroluminescent element. If airtightness is maintained, an appropriate material can be used. Reference numeral 8 denotes a drive power supply for current injection.

In the organic electroluminescent device to which the polyarylene compound according to the present invention is applied, the organic layer has an organic laminated structure (single heterostructure) in which a hole transport layer and an electron transport layer are laminated. The polyarylene compound according to the present invention may be used as a material for forming the hole transport layer or the electron transport layer. Alternatively, the organic layer has an organic laminated structure (double hetero structure) in which a hole transport layer, a light-emitting layer, and an electron transport layer are sequentially laminated, and a material for forming the light-emitting layer according to the present invention Polyarylene compounds may be used.

An example of an organic electroluminescent device having such an organic laminated structure is shown in FIG.
It has a laminated structure in which a translucent anode 2, an organic layer 5 a including a hole transport layer 6 and an electron transport layer 7, and a cathode 3 are sequentially laminated, and this laminated structure is sealed with a protective film 4. This is an organic electroluminescent device C having a single hetero structure.

As shown in FIG. 8, in the case of a layer configuration in which the light emitting layer is omitted, emitted light 20 of a predetermined wavelength is generated from the interface between the hole transport layer 6 and the electron transport layer 7. These emitted lights are observed from the substrate 1 side.

FIG. 9 shows a light-transmitting anode 2, an organic layer 5 b composed of a hole transport layer 10, a light-emitting layer 11 and an electron transport layer 12, and a cathode 3 on a light-transmitting substrate 1. Are sequentially laminated, and this laminated structure is sealed with a protective film 4 to form an organic electroluminescent device D having a double hetero structure.

In the organic electroluminescent device shown in FIG. 9, when a DC voltage is applied between the anode 2 and the cathode 3, the holes injected from the anode 2 pass through the hole transport layer 10, and The electrons injected from 3 reach the light emitting layer 11 via the electron transport layer 12 respectively. As a result, electron / hole recombination occurs in the light emitting layer 11 to generate singlet excitons, and the singlet excitons emit light of a predetermined wavelength.

In each of the organic electroluminescent elements C and D described above, the substrate 1 can be made of a light-transmissive material such as glass or plastic. In addition, the substrate may be shared when used in combination with another display element or when the stacked structures shown in FIGS. 8 and 9 are arranged in a matrix. In addition, both elements C and D are:
Either a transmission type or a reflection type structure can be adopted.

The anode 2 is a transparent electrode and is made of ITO.
(Indium tin oxide), SnO ₂ or the like can be used. A thin film made of an organic substance or an organometallic compound may be provided between the anode 2 and the hole transport layer 6 (or the hole transport layer 10) for the purpose of improving the charge injection efficiency. When the protective film 4 is formed of a conductive material such as a metal,
An insulating film may be provided on the side surface of the anode 2.

The organic layer 5a in the organic electroluminescent device C is an organic layer in which a hole transport layer 6 and an electron transport layer 7 are laminated, and one or both of them are a polyarylene compound according to the present invention. And the light-emitting hole transport layer 6 or the electron transport layer 7 may be used. Organic electroluminescent device D
Is an organic layer in which a hole transport layer 10, a light emitting layer 11 containing a polyarylene compound based on the present invention, and an electron transport layer 12 are laminated.
Various laminated structures can be adopted. For example, one or both of the hole transport layer and the electron transport layer may have a light emitting property.

It is particularly preferable that the hole transport layer 6, the electron transport layer 7, and the light emitting layer 11 are layers composed of the polyarylene compound according to the present invention.
It may be formed only from the polyarylene compound according to the present invention, or may be co-deposited with the polyarylene compound according to the present invention and another hole or electron transporting material (eg, aromatic amines and pyrazolines). May be formed. Further, in the hole transport layer, a hole transport layer in which a plurality of types of hole transport materials are stacked may be formed in order to improve hole transport performance.

In the organic electroluminescent device C, the light emitting layer may be the electron transporting light emitting layer 7, but depending on the voltage applied from the power supply 8, the light emitting layer may emit light at the hole transporting layer 6 or its interface. There is. Similarly, in the organic electroluminescent device D, the light emitting layer may be the electron transport layer 12 or the hole transport layer 10 other than the layer 11. In order to improve the light emitting performance, it is preferable that the light emitting layer 11 using at least one kind of fluorescent material is sandwiched between the hole transport layer and the electron transport layer. Alternatively, a structure in which this fluorescent material is contained in the hole transporting layer or the electron transporting layer, or both of them may be configured. In such a case, in order to improve the luminous efficiency, a thin film (such as a hole blocking layer or an exciton generation layer) for controlling the transport of holes or electrons can be included in the layer configuration.

The material used for the cathode 3 is L
An alloy of an active metal such as i, Mg, Ca or the like and a metal such as Ag, Al, In or the like can be used, and a structure in which these metal layers are laminated may be used. Incidentally, by appropriately selecting the thickness and material of the cathode, an organic electroluminescent device suitable for the intended use can be produced.

The protective film 4 functions as a sealing film, and by having a structure that covers the entire organic electroluminescent element, the charge injection efficiency and the luminous efficiency can be improved. As long as the airtightness is maintained, the material can be appropriately selected, such as a single metal such as aluminum, gold, and chromium, or an alloy.

The current applied to each of the above-mentioned organic electroluminescent elements is usually a direct current, but a pulse current or an alternating current may be used. The current value and the voltage value are not particularly limited as long as they are within a range not passing through the element. However, in consideration of the power consumption and the life of the organic electroluminescent element, it is desirable to emit light efficiently with as little electric energy as possible.

Next, FIG. 10 shows an example of the configuration of a flat display using an organic electroluminescent element to which the polyarylene compound according to the present invention is applied. As shown in the figure, for example, in the case of a full-color display, an organic layer 5 (5a, 5b) capable of emitting three primary colors of red (R), green (G) and blue (B)
Is disposed between the cathode 3 and the anode 2. The cathode 3 and the anode 2 can be provided in a stripe shape crossing each other, and are selected by the luminance signal circuit 14 and the control circuit 15 with a built-in shift register, and a signal voltage is applied to each of them. The organic layer at a position (pixel) where the anode 3 and the anode 2 intersect is configured to emit light. As this driving method, a simple matrix system or an active matrix system can be used.

That is, FIG. 10 shows, for example, an 8 × 3 RGB simple matrix in which a laminate 5 comprising a hole transport layer and at least one of a light emitting layer and an electron transport layer is placed between the cathode 3 and the anode 2. 8 and 9.
reference). The cathode and the anode are both patterned in stripes, and are orthogonal to each other in a matrix,
The control circuits 15 and 14 with a built-in shift register apply a signal voltage in time series, and emit light at the intersection. The EL element having such a configuration
The display of characters, signal course, can also be used as an image reproducing apparatus. Further, it is possible to configure a multi-color or full-color all-solid-state flat panel display by arranging stripe patterns of the cathode 3 and the anode 2 for each color of red (R), green (G), and blue (B). Become.

[0036]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to the following Examples.

Example 1 The desired polyarylene of the above structural formula (1) was synthesized by a Suzuki coupling reaction using a palladium catalyst. First, 2,2 ', 7,7'-tetrabromo-9,9'-spirobifluorene (900 mg, 1.4
2 mmol), 1-naphthaleneboronic acid (1.03 g,
5.98 mmol), toluene (50 ml), 2N potassium carbonate aqueous solution (50 ml), tetrakistriphenylphosphine palladium (0) (84.2 mg, 71.
(2 mmol) was heated and stirred at 100 ° C. for 12 hours.

The progress of the reaction was confirmed by TLC (thin layer liquid chromatography), and the reaction mixture was filtered using alumina. The obtained mixture was extracted with chloroform, and the organic layer was washed successively with water and saturated saline, dried over anhydrous sodium sulfate, and concentrated under reduced pressure. The residue was purified twice by column chromatography (carrier: silica gel, developing solvent: chloroform / hexane = 3/1 to 1/1), recrystallized from chloroform / hexane, and polyarylene represented by the structural formula (1) ( (840 mg, 72%) as a white powder.

The sample for evaluation was further purified by column chromatography (carrier: silica gel, developing solvent: chloroform / hexane = 4/1 to 1/1) and recrystallized from chloroform-ether to obtain 355 mg. Analytical data for this product was as follows:

NMR δ / ppm: 7.13 (m, 4H), 7.03
(M, 4H), 7.35-7.55 (m, 16H), 7.76-7.88 (m, 12H), 7.92
(m, 4H) The NMR spectrum and the DSC chart are shown in FIGS. However, the DSC measurement was performed in the sequence shown by 1) to 5) in the figure (the same applies hereinafter). FIG. 4 shows the absorbance and the fluorescence spectrum.

Comparative Example 1 As a measurement sample, a spiro-type polyarylene compound represented by the above structural formula (3) was subjected to DSC measurement. The measurement conditions were the same as those described in Example 1 above.

FIG. 3 shows the results of Comparative Example 1. As for the known polyarylene compound represented by the structural formula (3), no glass transition point was observed, and Tm (melting point): 385 ° C. was observed. . The absorbance and the fluorescence spectrum are shown in FIG.

From the above, the first embodiment according to the present invention is described.
It was found that the polyarylene compound of Comparative Example 1 exhibited thermophysical properties rich in amorphous properties as compared with the polyarylene compound of Comparative Example 1. Moreover, after melting, it became a syrup and exhibited an amorphous appearance.

Example 2 In this example, the polyarylene represented by the structural formula (1) obtained as described above was used as an electron transporting layer (also serving as a light emitting layer), and a single-layered structure as shown in FIG. This is an example in which an organic electroluminescent device having a hetero structure is manufactured.

More specifically, the following layers (1) to (2) were sequentially formed at different thicknesses on a glass substrate to produce an organic electroluminescent device serving as a blue light emitting device. At this time, first, the anode material is formed by sputtering, and then the anode material is 2 mm × 2 m
An insulating film (silicon oxide film) having an opening window exposed in the range of m was formed on the substrate. Next, from the hole injection layer material to the buffer layer material was formed on the anode material by vacuum deposition from above the deposition mask. Thereafter, the deposition mask was removed, and a cathode material was laminated on the buffer layer material in a vacuum state. Anode: ITO: 190 nm, hole injection layer: 2-TNATA [4,4 ', 4 "-tris (2-naphthylphenylamino) triphenylamine] ... 20 nm, hole transport layer: represented by the following structural formula (4) Triphenylamine tetramer represented ... 50 nm, electron transporting light emitting layer: polyarylene represented by the structural formula (1) synthesized as in Example 1 ... 40 n
m, buffer layer: lithium oxide ... 0.5 nm, cathode: aluminum ... 200 nm.

Embedded image Structural formula (4):

The characteristics of the organic electroluminescent device thus manufactured are described below.
As a result, the emission color was blue.
As a result, the emission spectrum shown in FIG.
There is a peak nearby. ) Is shown.
Ratio using the polyarylene compound of Comparative Example 1 in the same manner
The emission spectrum of the organic electroluminescent device of Comparative Example 2 is shown in FIG.
Similarly, the two peaks are separated. In addition,
Flow density 25mA / cm ^TwoThe luminance at the time of is 50 cd / m^TwoIn
It was confirmed that sufficient luminance was obtained. Spectrometry
Uses a photodiode array manufactured by Otsuka Electronics Co., Ltd. as a detector
A spectroscope was used.

[0047]

According to the present invention, the general formula (1)
The polyarylene compound of the following, by the selection of its substituent,
It shows a clearer glass transition temperature than conventional materials and has thermal stability suitable for vacuum deposition.

[Brief description of the drawings]

FIG. 1 is a diagram showing an NMR spectrum of a polyarylene compound according to an example of the present invention.

FIG. 2 is a DSC characteristic diagram of the same polyarylene compound.

3 is a DSC characteristic diagram of polyarylene compounds according to Comparative Example.

FIG. 4 is a spectrum diagram showing the results of spectroscopic measurement of a polyarylene compound according to another embodiment of the present invention, together with its absorbance.

FIG. 5 is a spectrum diagram showing the results of spectroscopic measurement of a polyarylene compound of a comparative example together with its absorbance.

FIG. 6 is a schematic cross-sectional view of main parts when a polyarylene compound according to the present invention is used in an organic electroluminescent device.

FIG. 7 is a schematic cross-sectional view of a main part when a polyarylene compound according to the present invention is used in another organic electroluminescent device.

FIG. 8 is a schematic cross-sectional view of a main part when a polyarylene compound according to the present invention is used in another organic electroluminescent device.

FIG. 9 is a schematic cross-sectional view of a main part when a polyarylene compound according to the present invention is used in still another organic electroluminescent device.

FIG. 10 is a configuration diagram of a full-color flat display using an organic electroluminescent element.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Transparent electrode (anode), 3 ... Cathode, 4 ... Protective film, 5 5a, 5b ... Organic layer, 6 ... Hole transport layer, 7 ... Electron transport layer, 8 ... Power supply, 10 ... Positive Hole transporting layer, 11 light emitting layer, 12 electron transporting layer, 14 luminance signal circuit, 15 control circuit, 20 light emission, A, B, C, D organic electroluminescent element

Continuation of the front page (72) Inventor Shinichiro Tamura 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo F-term in Sony Corporation (reference) 3K007 AB02 AB03 AB04 AB11 AB18 CA01 CB01 DA01 DB03 EB00 4H006 AA01 AB64 4J032 CA03 CA12 CA14 CB03 CD02 CG01

Claims (3)

[Claims] 1. A polyarylene compound represented by the following general formula (1). Embedded image General formula (1): (However, in the general formula (1), R ¹ , R ² , R ³ ,
R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ and R
¹² may be each independently an alkyl group having 10 or less carbon atoms. Further, at least one of the benzene rings in the general formula (1) is condensed with at least one benzene ring, and n ¹ , n ² , n ³ , n ⁴ , n ⁵ , n ⁶ , and n ⁷ And n ⁸ are each independently an integer from 0 to 5. ) 2. The method according to claim 1, which is represented by the following general formula (2).
The polyarylene compound described in 1. Embedded image General formula (2): 3. The polyarylene compound according to claim 2, represented by the following structural formula (1) or (2). Embedded image Structural formula (1): Embedded image Structural formula (2):