JP2005240008A - Organic light-emitting material and organic electroluminescent element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic light-emitting material having high light-emitting efficiency and an excellent light-emitting lifetime, and to provide an organic electroluminescent element by using the same. <P>SOLUTION: The organic light-emitting material for the organic electroluminescent element is expressed by formula (1) (A<SP>1</SP>to A<SP>20</SP>are each H, a halogen, hydroxy, a substituted or unsubstituted carbonyl composed of 20 or less carbon atoms, a substituted or unsubstituted carbonyl ester composed of 20 or less carbon atoms, a substituted or unsubstituted alkyl composed of 20 or less carbon atoms, a substituted or unsubstituted alkenyl composed of 20 or less carbon atoms, a substituted or unsubstituted alkoxyl composed of 20 or less carbon atoms, a substituted or unsubstituted aryl composed of 30 or less carbon atoms, a substituted or unsubstituted heterocyclic composed of 30 or less carbon atoms, cyano, nitro or silyl). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an organic light emitting material and an organic electroluminescent element.

  In recent years, light and highly efficient flat panel displays have been actively researched and developed, for example, as screen displays for computers and televisions. The most representative display device, a cathode ray tube (CRT), is currently used most frequently as a display because of its high brightness and good color reproducibility. However, it is bulky, heavy and has high power consumption. .

  In addition, liquid crystal displays such as active matrix driving have been commercialized as lightweight and highly efficient flat panel displays. However, the liquid crystal display has a narrow viewing angle and is not self-luminous, so the backlight consumes a lot of power in an environment where the surroundings are dark, and the high-definition high-speed video signal expected to be put to practical use in the future. In addition, there are problems such as not having sufficient response performance. In particular, it is difficult to produce a display with a large screen size, and there are problems such as high cost.

  Thus, as a flat panel display that can solve these problems, an organic electroluminescent element (so-called organic EL element) using an organic light emitting material has recently been attracting attention. That is, by using an organic compound as a light-emitting material, it is expected to realize a flat panel display that is self-luminous, has a high response speed, and has no viewing angle dependency.

  A general configuration of an organic electroluminescent element is formed by sandwiching an organic layer containing an organic light emitting material that emits light by passing a current between a light transmitting anode and a cathode made of a metal material. As the historical background of this organic electroluminescent device, first, the organic layer was provided with a two-layer structure of a thin film made of a hole transporting material and a thin film made of an electron transporting material, and sandwiched between the organic layers. An element structure has been developed that emits light by recombination of holes and electrons injected into the organic layer from the anode and the cathode, respectively (for example, see Non-Patent Document 1 below).

  Thereafter, an organic electroluminescent device having an organic layer having a three-layer structure of a hole transport material, a light emitting material, and an electron transport material was developed (for example, see Non-Patent Document 2 below), and a light emitting material was further incorporated in the electron transport material. The element structure etc. which were included were developed (for example, refer the following nonpatent literature 3). These studies have verified the possibility of light emission at low voltage and high brightness in organic electroluminescent devices, and research and development has been very active in recent years.

  FIG. 1 is a cross-sectional view showing one configuration example of such an organic electroluminescent element. The organic electroluminescent element 1 shown in this figure is provided on a transparent substrate 2 made of glass or the like, for example, and an anode 3 and an anode 3 made of ITO (Indium Tin Oxide: transparent electrode) provided on the substrate 2. The organic layer 4 is provided on the organic layer 4 and the cathode 5 is provided on the organic layer 4. The organic layer 4 has a configuration in which a hole injection layer 4a, a hole transport layer 4b, and an electron transporting light emitting layer 4c are sequentially stacked from the anode 3 side. In this organic electroluminescent element 1, electrons injected from the cathode 5 and holes injected from the anode 3 are recombined in the light emitting layer 4c, and light generated during the recombination is transmitted through the anode 3 to the substrate. It is taken out from the 2 side.

  As the organic electroluminescent element 1, in addition to the element having such a configuration, a structure in which a cathode, an organic layer, and an anode are sequentially laminated in order from the substrate side, or an upper electrode (upper part as a cathode or an anode) There is also a so-called top emission type organic electroluminescent element in which light is extracted from the upper electrode side opposite to the substrate by constituting the electrode) with a transparent material.

  In particular, in an active matrix type display device in which a thin film transistor (TFT) is provided on a substrate, a so-called TAC (Top) in which a top emission organic electroluminescence element is provided on a substrate on which a TFT is formed. Emitting Adoptive Current drive) structure is advantageous in improving the aperture ratio of the light emitting portion.

  Various studies have been made on the organic light-emitting material in the organic electroluminescent device having such a configuration, and in particular, improvements have been made to styryl allene or anthracene derivatives for blue color-developing materials (for example, the following non-patent documents). 4).

  In addition, an organic light emitting material having a fluoranthene structure has been reported as a blue to green organic light emitting material. Typical derivatives thereof include fluoranthene having an amino group or an aryl group (for example, Patent Documents 1 to 4 below), and compounds having a benzofluoranthene structure as a substituent (for example, Patent Documents 5 and 6 below). It is shown. Furthermore, although there has been no report on an unsubstituted bifluoranthene compound applied as an organic light-emitting material for an organic electroluminescence device, its synthesis and spectroscopic studies are already known (for example, the following non-patent documents) Reference 5).

Applied Physics Letters (USA) 1987, 51, 12, p. 913-915 Japanese Journal of Applied Physics, 1988, Vol. 27, No. 2, p. 269-271 Journal of Applied Physics (USA) 1989, 65, 9, p. 3610-3616 Materials Science and Engineering: R: Reports Volume 39, Issues 5-6, Pages 143-222, 2002 Journal of the American Chemical Society (USA) 1968, Vol. 90, No. 3, p. 566-569 JP-A-10-125467 Japanese Patent Laid-Open No. 10-189248 JP 2002-43058 A JP 2003-81924 A JP 2001-257074 A JP 2002-69044 A

  By the way, since the organic electroluminescent element described above is a self-luminous element, when a display device is configured using the organic electroluminescent element, it is most important to make the organic electroluminescent element longer in life and to ensure reliability. One. For this reason, as described above, although research on organic materials constituting the organic electroluminescent device has been pursued, nothing has yet reached practicality in terms of light emission efficiency and light emission lifetime, and further improvements in device physical properties have been achieved. There is a need for improvement.

  Accordingly, an object of the present invention is to provide an organic light emitting material having high light emission efficiency and excellent light emission lifetime, and an organic electroluminescent device using the same.

The organic light-emitting material of the present invention for achieving such an object is an organic light-emitting material for an organic electroluminescent element, and is represented by the following general formula (1).

However, in the general formula (1), A ^{1 to} A ²⁰ are each independently hydrogen, halogen, hydroxyl group, substituted or unsubstituted carbonyl group having 20 or less carbon atoms, substituted or unsubstituted carbon group having 20 or less carbon atoms. Carbonyl ester group, substituted or unsubstituted alkyl group having 20 or less carbon atoms, substituted or unsubstituted alkenyl group having 20 or less carbon atoms, substituted or unsubstituted alkoxyl group having 20 or less carbon atoms, substituted or unsubstituted 30 carbon atoms or less An unsubstituted aryl group, a substituted or unsubstituted heterocyclic group having 30 or less carbon atoms, a cyano group, a nitro group, or a silyl group is shown.

  The carbonyl group includes an aldehyde group, a ketone group, and a carboxyl group. The alkyl group includes a linear alkyl group, a branched alkyl group, and a cyclic alkyl group.

  In addition, as the substituents for the above-described substituents, that is, a carbonyl group, a carbonyl ester group, an alkyl group, an alkenyl group, an alkoxyl group, an aryl group, and a heterocyclic group, a halogen, a hydroxyl group, Examples thereof include a carbonyl group, a carbonyl ester group, a cyclic alkyl group, an alkenyl group, an alkoxy group, an aryl group, a heterocyclic group, a cyano group, a nitro group, and a silyl group.

In particular, at least one of A ^{1 to} A ^{20 in} the general formula (1) is substituted with a substituent selected from an alkyl group, an alkenyl group, an alkoxy group, a heterocyclic group, or an aryl group. preferable.

  Moreover, this invention is also an organic electroluminescent element (organic EL element) using such an organic luminescent material. An organic electroluminescent element has an organic layer sandwiched between an anode and a cathode, and this organic layer is formed using an organic light emitting material represented by the above general formula (1). More specifically, the organic layer includes a light emitting layer configured using the organic light emitting material represented by the general formula (1). In addition, it is preferable that the content rate of the organic luminescent material shown by General formula (1) in a light emitting layer is 20 volume% or less.

  The organic light-emitting material of the present invention having the above-described configuration has the above-described fluoranthene structure in the molecule, and thus has good thermal properties, excellent external force and thermal durability, and depends on voltage. It also has stability in fluctuating power. In particular, crystallization is unlikely to occur due to the effect of increasing the molecular weight by dimerizing fluoranthene into bifluoranthene. In addition, electroluminescence based on the high fluorescence characteristic of fluoranthene can be obtained.

  Therefore, the organic electroluminescent element of the present invention in which the organic layer is formed using such an organic light emitting material has excellent durability of the organic layer when driven for a long time. In addition, it also exhibits excellent light emission characteristics over a blue to green light emission region.

  As described above, by using the organic light emitting material of the present invention for the organic layer of the organic electroluminescent element, it is possible to improve the durability of the organic layer and to improve the light emission lifetime in the organic electroluminescent element. At the same time, it is possible to improve the light emission efficiency particularly in the blue to green light emission region. As a result, a full color display with high color reproducibility can be realized by configuring a pixel by combining a red light emitting element and a blue light emitting element together with the organic electroluminescent element.

  Hereinafter, the structures of the organic light emitting material and the organic electroluminescent element of the present invention will be described in more detail.

<Organic luminescent material>
The organic light-emitting material of the present invention represented by the general formula (1) described above is a bifluoranthene compound used for the organic layer of the organic electroluminescent element. The bifluoranthene compound has a plurality of isomers at each fluoranthene bonding position, but the organic light-emitting material of the present invention includes all the structural isomers. That is, the organic light-emitting material of the present invention includes all of the following 15 combinations of substitutional isomers in view of the molecular symmetry of bifluoranthene (see Table 1 below).

a) 1, 1 ′ bond; bond at A ³ site and A ⁶ site of general formula (1) [Structural Formula (6)]
b) 2, 2 ′ bond; bond at A ⁴ site and A ⁵ site of general formula (1) [Structural formula (2)]
c) 3, 3 ′ bond; bond at A ¹⁴ site and A ¹⁵ site of general formula (1) [Structural formula (1)]
d) 7, 7 ′ bond; bond at A ² site and A ⁷ site of general formula (1) [Structural Formula (7)]
e) 8, 8 ′ bond; bond at A ¹ site and A ⁸ site of general formula (1) [Structural Formula (8)]
f) 1, 2 ′ bond; bond at A ³ site and A ⁵ site of general formula (1) [Structural formula (5)]
g) 1, 3 ′ bond; bond at A ³ site and A ¹³ site of general formula (1) [Structural formula (4)]
h) 1, 7 ′ bond; bond at A ³ site and A ⁷ site of general formula (1) [Structural formula (13)]
i) 1,8 ′ bond; bond at A ³ site and A ⁸ site of general formula (1) [Structural Formula (14)]
j) 2, 3 ′ bond; bond at A ⁴ site and A ¹³ site of general formula (1) [Structural formula (3)]
k) 2, 7 ′ bond; bond at A ⁴ site and A ⁷ site of general formula (1) [Structural formula (11)]
l) 2,8 ′ bond; bond at A ⁴ site and A ⁸ site of general formula (1) [Structural formula (12)]
m) 3, 7 ′ bond; bond at A ¹⁵ site and A ⁷ site of general formula (1) [Structural formula (9)]
n) 3, 8 ′ bond; bond at A ¹⁵ site and A ⁸ site of general formula (1) [Structural Formula (10)]
o) 7, 8 ′ bond; bond at A ² site and A ⁸ site of general formula (1) [Structural Formula (15)]

The structural formulas (1) to (15) in Table 1 above show the substitution pattern of bifluoranthene, which is the organic luminescent material of the present invention, and the unsubstituted fluoranthene compound, which is the organic luminescent material of the present invention. The bifluoranthene compound is shown. In the organic light-emitting material of the present invention, the portions corresponding to the substituents A ^{1 to} A ²⁰ in the general formula (1) in these compounds (1) to (15) are independently substituted with the above-described substituents. May be.

  Hereinafter, an example of the organic light-emitting material of the present invention in which the unsubstituted compound represented by the structural formulas (1) to (15) is substituted with each substituent is shown.

For example, as an example in which the unsubstituted compound represented by Structural Formula (1) in Table 1 is substituted with a substituent, compounds represented by Structural Formulas (1) -1 to (1) -17 in Table 2 below can be given. Among these, structural formula (1) -1, structural formula (1) -2, and structural formula (1) -3 are compounds in which each part is substituted with a linear alkyl group. Structural formulas (1) -4 and (1) -5 are compounds in which each part is substituted with a branched alkyl group.

Furthermore, as an example in which the unsubstituted compound represented by Structural Formula (2) in Table 1 is substituted with a substituent, compounds represented by Structural Formulas (2) -1 to (2) -10 in Table 3 below can be given. Among these, structural formula (2) -1 is a compound in which each part is substituted with a linear alkyl group. Structural formula (2) -2 is a compound in which each part is substituted with a branched alkyl group.

And as an example which substituted the unsubstituted compound shown by Structural formula (7) of Table 1 with a substituent, the compound shown to Structural formula (7) -1-(7) -10 of following Table 4 is mentioned. Of these, the structural formula (7) -1 is a compound in which each part is substituted with a linear alkyl group. Structural formulas (7) -5 and (7) -8 are compounds in which each part is substituted with a linear alkyl group and an aromatic hydrocarbon group.

Furthermore, as an example in which the unsubstituted compound represented by Structural Formula (8) in Table 1 is substituted with a substituent, compounds represented by Structural Formulas (8) -1 to (8) -8 in Table 5 below can be given. Among these, structural formula (8) -1, structural formula (8) -2, and structural formula (8) -3 are compounds in which each part is substituted with a linear alkyl group. Structural formula (8) -4 is a compound in which each part is substituted with a branched alkyl group.

The organic light-emitting material of the present invention shown as an example above can be synthesized by various methods, and examples include the following methods a) to c).
a) A synthesis method in which a halogenated fluoranthene is coupled by a Grignard reaction using magnesium.
b) A method in which halogenated fluoranthene is coupled by the Ullmann reaction in the presence of a copper catalyst.
c) A method of synthesizing boronic acid or boronic acid esterified fluoranthene and halogenated fluoranthene by a transition metal catalyst typified by palladium (so-called Suzuki coupling reaction).

  The organic light-emitting material comprising the bifluoranthene compound of the present invention is used as a material constituting the organic layer of the organic electroluminescent element, and the purity of the organic light-emitting material may be increased before being subjected to the manufacturing process of the organic electroluminescent element. Preferably, the purity is 95% or more, more preferably 99% or more. As a method for obtaining such a high-purity organic compound, in addition to a recrystallization method, a reprecipitation method, which is a purification after the synthesis of the organic compound, or a column purification using silica or alumina, a known method by a sublimation purification or a zone melt method is used. High purity methods can be used.

  Further, by repeatedly performing these purification methods or combining different purification methods, the mixture of unreacted substances, reaction byproducts, catalyst residues, or residual solvents in the organic light-emitting material in the present invention is reduced, It becomes possible to obtain an organic electroluminescent element with more excellent device characteristics.

Further, this compound is composed of the organic light-emitting material, particularly by suppressing the deterioration reaction from the oxidation and decomposition by taking the following storage methods a) to c) from the external factors such as light and oxygen. In the organic electroluminescence device, not only provides superior light emission characteristics, but also exhibits an effect in reducing the load on the manufacturing apparatus.
a) After synthesizing the organic light emitting material, immediately leave it in a cool place. The storage temperature is preferably in the range of -100 ° C to 100 ° C, more preferably in the temperature range of -50 ° C to 50 ° C.
b) After synthesizing the organic light emitting material, immediately store it in a light-shielding container.
c) After synthesizing the organic light emitting material, the synthesized organic light emitting material is stored in an inert gas atmosphere such as nitrogen, carbon dioxide, argon or the like.

  Since the organic light-emitting material of the present invention described above has a fluoranthene structure in the molecule, it has good thermal properties, is excellent in external force and thermal durability, and has a variable force due to voltage. It has stability. In particular, crystallization is unlikely to occur due to the effect of increasing the molecular weight by dimerizing fluoranthene into bifluoranthene. In addition, electroluminescence based on the high fluorescence characteristic of fluoranthene can be obtained.

  Therefore, by using the organic light-emitting material having such a structure in the organic layer of the organic electroluminescence device described below, the durability of the organic layer can be improved and the emission lifetime of the organic electroluminescence device can be improved. In addition, it becomes possible to improve the light emission efficiency particularly in the blue to green light emission region.

  Further, by introducing an appropriate substituent having a defined number of carbon atoms as described above into this bifluoranthene, it becomes possible to further improve the light emission efficiency and the light emission lifetime. In particular, by interstituting one or more of the substitution sites in bifluoranthene with a substituent selected from an alkyl group, an alkoxy group, an alkenyl group, a heterocyclic group or an aryl group, the intermolecular interaction is alleviated and light emission is achieved. It is effective for controlling crystallization related to device characteristics and suppressing bimolecular excitation.

  Moreover, the organic light-emitting material comprising the bifluoranthene compound according to the present invention has both electron transport performance and hole transport performance. For this reason, as will be described in detail below, among the organic layers of the organic electroluminescence device, it can be used as a light emitting layer that also serves as an electron transporting layer or as a light emitting layer that also serves as a hole transporting layer. . Moreover, it is also possible to use a structure in which the bifluoranthene compound according to the present invention is sandwiched between an electron transport layer and a hole transport layer as a light emitting layer.

<Organic electroluminescent device>
Next, the structure of the organic electroluminescent element (organic EL element) using the organic luminescent material described above will be described in detail with reference to FIG.

  The organic electroluminescent element 11 shown in FIG. 2 is configured as a top emission type element in which an anode 13, an organic layer 14, and a cathode 15 are laminated in this order on a substrate 12, and light is extracted from the side opposite to the substrate 12. ing.

  Here, the substrate 12 is a support on which the organic electroluminescence elements 11 are arranged and formed on one main surface side thereof, and may be a well-known one, for example, made of quartz, glass, metal foil, or resin. Of these, quartz and glass are preferable. In the case of resin, methacrylic resins represented by polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), polyethylene naphthalate (PEN) are used. ), Polyesters such as polybutylene naphthalate (PBN), polycarbonate resin, and the like, but it is necessary to perform a laminated structure and surface treatment that suppress water permeability and gas permeability.

The anode 13 provided on the substrate 12 has a high work function from the vacuum level of the electrode material in order to inject holes efficiently, for example, chromium (Cr), molybdenum (Mo), tungsten (W). , Copper (Cu), silver (Ag), gold (Au), alloys of tin oxide (SnO ₂ ) and antimony (Sb), alloys of zinc oxide (ZnO) and aluminum (Al), and these metals Or an oxide of an alloy is used alone or in a mixed state. The anode 13 can be produced by, for example, a sputtering method.

  When the driving method of the display device configured using the organic electroluminescent element 11 is an active matrix method, the anode 13 is patterned for each pixel and connected to a driving thin film transistor provided on the substrate 12. It is provided in the state that was done. Further, although not shown here, an insulating film is provided on the anode 13, and the surface of the anode 13 of each pixel is exposed from the opening of the insulating film. And

  And the organic layer 14 provided on this anode 13 turns into a layer comprised using the organic luminescent material peculiar to this invention. The organic layer 14 is formed, for example, by laminating four layers of a hole injection layer 14a, a hole transport layer 14b, a light emitting layer 14c, and an electron transport layer 14d in this order from the anode 13 side.

  And in the organic electroluminescent element 11 of this invention, at least one layer of the positive hole transport layer 14b, the light emitting layer 14c, and the electron carrying layer 14d is comprised using the organic luminescent material mentioned above. In particular, the light emitting layer 14c is preferably configured using the organic light emitting material described above.

  Here, the hole injection layer 14a and the hole transport layer 14b are for increasing the efficiency of hole injection into the light emitting layer 14c, respectively. Examples of the material for the hole injection layer 14a or the hole transport layer 14b include benzine, styrylamine, triphenylamine, porphyrin, triazole, imidazole, oxadiazole, polyarylalkane, phenylenediamine, and arylamine. , Oxazole, anthracene, fluorenone, hydrazone, stilbene, or derivatives thereof, or heterocyclic conjugated monomers, oligomers or polymers such as polysilane compounds, vinylcarbazole compounds, thiophene compounds or aniline compounds Can do.

  Specifically, α-naphthylphenylphenylenediamine, porphyrin, metal tetraphenylporphyrin, metal naphthalocyanine, 4,4,4-tris (3-methylphenylphenylamino) triphenylamine, N, N, N ′, N '-Tetrakis (p-tolyl) p-phenylenediamine, N, N, N', N'-tetraphenyl-4,4'-diaminobiphenyl, N-phenylcarbazole, 4-di-p-tolylaminostilbene, poly (Paraphenylene vinylene), poly (thiophene vinylene), poly (2,2′-thienylpyrrole) and the like are exemplified, but not limited thereto.

  The light emitting layer 14c is a region where holes and electrons are injected from each of the anode 13 and the cathode 15 when a voltage is applied by the anode 13 and the cathode 15, and these are recombined. Such a light emitting layer 14c is made of a material having high luminous efficiency, for example, an organic material such as a low molecular fluorescent dye, a fluorescent polymer, or a metal complex. Specifically, for example, anthracene, naphthalene, indene, phenanthrene, pyrene, naphthacene, triphenylene, chrysene, perylene, picene, fluoranthene, acephenanthrylene, pentaphen, pentacene, coronene, butadiene, coumarin, acridine, stilbene, or these Derivatives thereof, tris (8-quinolinolato) aluminum complex, bis (benzoquinolinolato) beryllium complex, tri (dibenzoylmethyl) phenanthroline europium complex ditoluyl vinylbiphenyl.

  Then, the above-described organic light-emitting material described using the general formula (1) is added as a guest material (or dopant material) to the light-emitting layer 14c. In this case, the amount of the organic light emitting material added is 20% by volume or less.

  The electron transport layer 14d is for transporting electrons injected from the cathode 15 to the light emitting layer 14c. Examples of the material for the electron transport layer 14d include quinoline, perylene, bisstyryl, pyrazine, triazole, oxazole, oxadiazole, fluorenone, and derivatives thereof. Specific examples include tris (8-hydroxyquinoline) aluminum (abbreviated as Alq3), anthracene, naphthalene, phenanthrene, pyrene, chrysene, perylene, butadiene, coumarin, acridine, stilbene, or derivatives thereof.

  Each of these layers can be formed by a method such as a vacuum deposition method or a spin coating method. In particular, in the formation of the light emitting layer 14c, a small amount of fluorescent molecules may be co-deposited when the light emitting layer 14c is formed for the purpose of controlling the emission spectrum of the light emitting layer 14c. In this case, for example, the light emitting layer 14c may be formed of an organic thin film containing a trace amount of an organic substance such as a naphthalene derivative, anthracene derivative, pyrene derivative, naphthacene derivative, berylene derivative, coumarin derivative, or pyran dye as a fluorescent molecule. .

  The organic layer 14 is not limited to such a layer structure, and has at least the light emitting layer 14c and the hole transport layer 14a or the hole injection layer 14b between the anode 13 and the light emitting layer 14c. If it is a structure, the laminated structure as needed can be selected.

  The light emitting layer 14c may be provided in the organic electroluminescent element 11 as a hole transporting light emitting layer or an electron transporting light emitting layer. Furthermore, each layer constituting the organic layer 14 described above, for example, the hole injection layer 14a, the hole transport layer 14b, the light emitting layer 14c, and the electron transport layer 14d may have a laminated structure including a plurality of layers.

  And the organic compound which comprises such an organic layer 14 has the transport ability of an electron or a hole (hole) besides using the compound which light-emits fluorescence and phosphorescence by applying an electric field. A compound is appropriately used.

  Next, the cathode 15 provided on the organic layer 14 having such a configuration has, for example, a two-layer structure in which a first layer 15a and a second layer 15b are stacked in this order from the organic layer 14 side.

The first layer 15a is made of a material having a small work function and good light transmittance. Examples of such a material include lithium oxide (Li ₂ O) which is an oxide of lithium (Li), cesium oxide (Cs ₂ O) which is an oxide of cesium (Cs), and further, these oxides. Mixtures can be used. Further, the first layer 15a is not limited to such a material. For example, alkaline earth metals such as calcium (Ca) and barium (Ba), alkali metals such as lithium and cesium, and indium ( In), magnesium (Mg), or other low work function metals, or oxides of these metals may be used alone or as a mixture or alloy of these metals and oxides with increased stability. .

  The second layer 15b is constituted by a thin film using a light-transmitting layer such as MgAg. The second layer 15b may be a mixed layer containing an organic material such as an aluminum quinoline complex, a styrylamine derivative, or a phthalocyanine derivative. In this case, a layer having optical transparency such as MgAg may be additionally provided as the third layer.

  Each layer constituting the cathode 15 can be formed by a technique such as vacuum deposition, sputtering, or plasma CVD. Further, when the driving method of the display device configured using the organic electroluminescent element 11 is an active matrix method, the cathode 15 is formed by an organic layer 14 and the above-described insulating film, which is not shown here, by an anode. 13 is formed in a solid film shape on the substrate 12 in an insulated state and used as a common electrode of each pixel.

  The cathode 15 is not limited to the above laminated structure. This laminated structure is necessary when functional separation of each electrode layer (for example, functional separation between an inorganic layer that promotes electron injection and an inorganic layer that controls the electrode) is performed. Therefore, it is possible to configure only the second layer 15b, or to form a transparent electrode such as ITO after the first layer 15a is formed. Needless to say, the structure should be taken.

  The current applied to the organic electroluminescent element 11 having the above-described configuration 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 the elements are not interposed. However, considering the power consumption and life of the organic electroluminescent element, it is desirable to efficiently emit light with as little electrical energy as possible.

  The organic electroluminescence device shown in FIG. 1 may have a configuration in which light is extracted from both the upper and lower sides by using a transparent electrode made of ITO or the like for the anode 13.

Further, when the organic electroluminescent element 11 has a cavity structure, the total film thickness of the organic layer 14 and the electrode layer made of a transparent material or a semi-transparent material is defined by the emission wavelength, and multiple interference is calculated. Will be set to the value derived from. In a so-called TAC (Top Emitting Adoptive Current drive) structure in which a top emission type organic electroluminescence device is provided on a substrate on which a TFT is formed, light is extracted to the outside by actively using this cavity structure. It is possible to improve efficiency and control the emission spectrum.

  According to the organic electroluminescent element 11 having the above-described configuration, the organic layer 14 is configured using the bifluoranthene compound described using the general formula (1). Thereby, the durability and stability of the organic layer 14 can be improved, and electroluminescence based on the high fluorescence characteristic of fluoranthene can be obtained. As a result, it is possible to improve the light emission lifetime in the organic electroluminescent element 11 and to improve the light emission efficiency particularly in the blue to green light emission region.

  A full color display with high color reproducibility can be realized by configuring a pixel by combining a red light emitting element and a blue light emitting element together with the organic electroluminescent element of the present invention.

  In the above embodiment, the organic light emitting material of the present invention is only used as a constituent material of a light emitting layer (including an electron transporting light emitting layer, a hole transporting light emitting layer, and a charge transporting light emitting layer). explained. However, the organic light-emitting material of the present invention is excellent in durability as described above and has an electron transport property and a hole transport property. This layer can be used as a material constituting a layer, for example, an electron transport layer, a hole transport layer, a hole injection layer, and the like. This makes it possible to improve durability in these layers.

  Further, the organic electroluminescence device of the present invention is not limited to the top emission type and application to a TAC structure using the top emission type, and an organic layer having at least a light emitting layer is sandwiched between an anode and a cathode. The present invention can be widely applied to the configuration. Therefore, the cathode, organic layer, and anode are laminated in order from the substrate side, and the electrode located on the substrate side (the lower electrode as the cathode or anode) is made of a transparent material so that it is on the opposite side of the substrate. The present invention can also be applied to a so-called transmissive organic electroluminescent element in which light is extracted from the upper electrode side of the above. Even if it is such a structure, the same effect can be acquired by using the organic luminescent material demonstrated using General formula (1) for an organic layer.

  Furthermore, the organic electroluminescent element of the present invention may be an element formed by a pair of electrodes (anode and cathode) and an organic layer sandwiched between the electrodes. For this reason, it is not limited to what comprised only a pair of electrode and organic layer, and other components (for example, an inorganic compound layer and an inorganic component) coexist in the range which does not impair the effect of this invention. Is not to be excluded.

  A synthesis example of the organic light emitting material of the present invention and an example of the organic electroluminescent element of the present invention using this organic light emitting material will be specifically described. Here, first, Synthesis Examples 1 to 6 of the organic light-emitting material of the present invention will be described, and then a procedure for producing an organic electroluminescent element using these organic light-emitting materials and an organic electroluminescent element of a comparative example, The evaluation results will be described.

<Synthesis example 1 of organic light emitting material>
As shown in the following reaction formula (1), 3,3′-bifluoranthene represented by the structural formula (1) in Table 1 was obtained.

That is, first, a 1000 ml three-necked flask equipped with a mechanical stirrer was sufficiently replaced with nitrogen, and then 500 ml of DMSO was added as a solvent, followed by 3-bromofluoranthene (C1) (29 g, 100 mmol), bispinacolate. Diboron (30 g, 120 mmol), potassium acetate (CH ₃ COOK) (20 g, 200 mmol), and tetrakis (triphenylphosphine) palladium [Pd (PPh ₃ ) ₄ ] (1.16 g, 1 mmol) were sequentially added to the solvent. . While stirring, the temperature was raised to 90 ° C. and reacted for 4 hours after reaching a steady state.

  After completion of the reaction, the solvent DMSO was removed by distillation under vacuum conditions, and then redissolved with toluene and washed with water. Subsequently, the toluene layer side was dried with sodium sulfate and then concentrated, and passed through a silica column with a mixed solvent of hexane: toluene = 8: 2 to obtain compound (C2) in a yield of 70%.

Subsequently, a 500 ml three-necked flask equipped with a mechanical stirrer was sufficiently replaced with nitrogen, and then synthesized as described above (C2) (16.0 g, 50 mmol), 3-bromofluoranthene (C1) (14 g, 50 mmol). ) Were added sequentially, and 100 mL of toluene was poured. While stirring, 150 mL of a 2.0 mol / liter Na ₂ CO ₃ aqueous solution was added, and the mixed solution was bubbled with nitrogen for 10 minutes to sufficiently exhaust the dissolved oxygen in the solution. Subsequently, tetrakis (triphenylphosphine) palladium [Pd (PPh ₃ ) ₄ ] (580 mg, 500 μmol) was added as a palladium catalyst component, and then the temperature was raised and reacted at the reflux temperature for 8 hours.

After completion of the reaction, the reaction mixture was cooled to room temperature, the organic layer was separated, washed 5 times with water, and the organic layer was dried over magnesium sulfate. The solution was concentrated and passed through a silica column with a mixed solvent of hexane: toluene = 8: 2 to obtain 16.5 g (yield 82%) of a white solid. As a result of measuring the obtained solid by ¹ H-NMR, ¹³ C-NMR, and FD-MS, it was confirmed to be 3,3′-bifluoranthene [Table 1 Structural Formula (1)], which is the target product. .

<Synthesis example 2 of organic light emitting material>
In the following manner, 2,2′-bifluoranthene represented by the structural formula (2) in Table 1 was obtained. That is, in the synthesis route and synthesis of Synthesis Example 1, the same operation as in Synthesis Example 1 was performed except that 3-bromofluoranthene (C1) was changed to 2-bromofluoranthene. 1 g was obtained. As a result of measuring the obtained solid by ¹ H-NMR, ¹³ C-NMR, and FD-MS, it was confirmed to be 2,2′-bifluoranthene [Table 1 Structural Formula (2)] which is the target product. .

<Synthesis example 3 of organic light emitting material>
In the following manner, 8,8′-bifluoranthene represented by the structural formula (8) in Table 1 was obtained. That is, in the synthesis route and synthesis of Synthesis Example 1, the same operation as in Synthesis Example 1 was carried out except that 3-bromofluoranthene (C1) was changed to 8-bromofluoranthene. 1 g was obtained. As a result of measuring the obtained solid by ¹ H-NMR, ¹³ C-NMR, and FD-MS, it was confirmed to be 8,8′-bifluoranthene [Table 1 Structural Formula (8)] which is the target product. .

<Synthesis Example 4 of Organic Light-Emitting Material>
As shown in the following reaction formula (2), 8,8′-diphenyl-3,3′-bifluoranthene represented by the structural formula (1) -6 in Table 2 was obtained.

That is, first, a 1000 ml three-necked flask equipped with a mechanical stirrer was sufficiently replaced with nitrogen, and then 500 ml of DMF was poured as a solvent, followed by 4,4′-dibromo-1,1′-bisnaphthalene (20 g, 50 mmol), 2-bromo-4,4′-biphenylboronic acid (30.4 g, 110 mmol), tricyclohexylphosphine (hereinafter referred to as P (Cy) ₃ ) (14 g, 50 mmol), 1,8-diazabicyclo [5 4.0] undecene (hereinafter referred to as DBU) (60 ml) and bisdibenzylideneacetone palladium (hereinafter referred to as Pd ₂ (dba) ₃ ) (7.1 g, 12.5 mmol) were sequentially added to the solvent. .

The temperature of the reaction solution was raised to 150 ° C. and carried out for 48 hours while refluxing. After completion of the reaction, washing was performed twice with 10% hydrochloric acid. Subsequently, it was washed with water, and the organic layer was dried over sodium sulfate and then concentrated, and passed through a silica column with a mixed solvent of hexane / toluene to obtain 18 g (yield 65%) of a white solid. As a result of measuring the obtained solid by ¹ H-NMR, ¹³ C-NMR, and FD-MS, 8,8′-diphenyl-3,3′-bifluoranthene [Table 2 Structural Formula (1)] -6].

<Synthesis example 5 of organic light emitting material>
As shown in the following reaction formula (3), 4,4′-di (1-naphthyl) -2,2′-bifluoranthene represented by the structural formula (2) -6 in Table 3 was obtained.

That is, first, a 1000 ml three-necked flask equipped with a mechanical stirrer was sufficiently replaced with nitrogen, and then 500 ml of DMF was poured as a solvent, followed by 4,7-dibromo-1,1′-bisnaphthalene (20 g, 50 mmol). ) (C3), 2-bromo-phenylboronic acid (12.5 g, 60 mmol), P (Cy) ₃ (14 g, 50 mmol), DBU (60 ml), and Pd ₂ (dba) ₃ (7.1 g, 12. 5 mmol) was sequentially added to the solvent.

  The temperature of the reaction solution was raised to 150 ° C. and carried out for 48 hours while refluxing. After completion of the reaction, washing was performed twice with 10% hydrochloric acid. Subsequently, it was washed with water, and the organic layer was dried over sodium sulfate and then concentrated, and passed through a silica column with a mixed solvent of hexane / toluene to obtain 12 g (yield 60%) of a yellow solid (C4).

Subsequently, a 1000 ml three-necked flask equipped with a mechanical stirrer was sufficiently replaced with nitrogen, 200 ml of DMSO was poured as a solvent, 6 g (15 mmol) of (C4) synthesized above was added, and then bispinaco Rate diboron (4.5 g, 18 mmol), potassium acetate (3 g, 30 mmol), and tetrakis (triphenylphosphine) palladium [Pd (PPh ₃ ) ₄ ] (175 mg, 150 μmol) were sequentially added to the solvent. The temperature was raised to 90 ° C. with stirring, and the reaction was allowed to proceed for 4 hours after reaching a steady state.

  After completion of the reaction, DMSO was removed by distillation, dissolved in toluene, and washed with water. Subsequently, the toluene layer side was dried with sodium sulfate and then concentrated, and passed through a silica column with a mixed solvent of hexane: toluene = 8: 2 to obtain compound (C5) in a yield of 80%.

Subsequently, after the 1000 ml three-necked flask equipped with a mechanical stirrer was sufficiently replaced with nitrogen, (C5) (5 g, 12 mmol) and (C4) (6 g, 15 mmol) synthesized above were sequentially added, and 50 mL of toluene was added. Was poured. While stirring, 60 mL of a 2.0 mol / L Na ₂ CO ₃ aqueous solution was added, and the mixed solution was bubbled with nitrogen for 10 minutes to sufficiently exhaust the dissolved oxygen in the solution. Subsequently, tetrakis (triphenylphosphine) palladium [Pd (PPh ₃ ) ₄ ] (125 mg, 0.1 mmol) was added as a palladium catalyst component, and then the temperature was raised and reacted at the reflux temperature for 8 hours.

After completion of the reaction, the reaction mixture was cooled to room temperature, the organic layer was separated, washed 5 times with water, and the organic layer was dried over magnesium sulfate. The solution was concentrated and then passed through a silica column with a toluene / ethyl acetate mixed solvent to obtain 4.5 g (yield 60%) of a white solid. As a result of measuring the obtained solid by ¹ H-NMR, ¹³ C-NMR, and FD-MS, 4,4′-di (1-naphthyl) -2, 2′-bifluoranthene [Table 3 It was confirmed that this is the structural formula (2) -6].

<Synthesis Example 6 of Organic Luminescent Material>
As shown in the following reaction formula (4), 3,3′-di (1-naphthyl) -7,7′-bifluoranthene represented by the structural formula (7) -7 in Table 4 was obtained.

That is, according to the synthesis method described in Synthesis Example 5, except that 4-bromo-1,1′-bisnaphthalene (C6) and 2,6-dibromophenylboronic acid were used as starting materials in Synthesis Example 5. The reaction proceeded. As a result of measuring the obtained solid by ¹ H-NMR, ¹³ C-NMR, and FD-MS, 3,3′-di (1-naphthyl) -7, 7′-bifluoranthene [Table 4], which is the target product, was obtained. It was confirmed that this is the structural formula (7) -7].

<Example 1>
Using 3,3′-bifluoranthene [Structural Formula (1) in Table 1] obtained in Synthesis Example 1, an organic electroluminescent device (see FIG. 2) was produced as follows.

First, a film (thickness: about 100 nm) made of chromium (Cr) is formed as an anode 13 on a substrate 12 made of a glass plate of 30 mm × 30 mm, and silicon dioxide (SiO ₂ ) is further deposited to deposit 2 mm × 2 mm. A cell for an organic electroluminescence device was produced by masking the region other than the light emitting region with an insulating film.

Next, as a hole injection layer 14a of the organic layer 14, a film made of m-MTDATA represented by the following structural formula (16) is formed to a thickness of 30 nm (deposition rate: 0.2 to 0.4 nm / sec). However, m-MTDATA is 4,4 ′, 4 ″ -tris (phenyl-m-tolylamino) triphenylamine.

Next, as the hole transport layer 14b, a film made of α-NPD represented by the following structural formula (17) was formed with a film thickness of 30 nm (deposition rate: 0.2 to 0.4 nm / sec). However, α-NPD is N, N′-bis (1-naphthyl) -N, N′-diphenyl [1,1′-biphenyl] -4,4′-diamine.

  On the hole injection layer 14a and the hole transport layer 14b thus formed, the 3,3′-bifluoranthene [Structural Formula (1) in Table 1] obtained in Synthesis Example 1 as the light-emitting layer 14c was obtained. Vapor deposition was performed with a film thickness of 40 nm.

Next, as the electron transport layer 14d, Alq3 (8-hydroxyquinoline aluminum) represented by the following structural formula (18) was deposited with a thickness of 20 nm.

As described above, after forming the organic layer 14 formed by sequentially laminating the hole injection layer 14a, the hole transport layer 14b, the light emitting layer 14c, and the electron transport layer 14d, as the first layer 15a of the cathode 15, A film made of Li ₂ O was formed with a film thickness of about 0.3 nm (deposition rate: 0.01 nm / sec.) By vacuum evaporation.

  Finally, a 10 nm-thick MgAg film was formed as the second layer 15b of the cathode 15 on the second layer 15a by a vacuum deposition method.

When the organic electroluminescence device produced in this way was driven by a direct current voltage, blue coloration was confirmed, and the light emission luminance was 1000 cd / m ² at a voltage of 6V. Further, when this light-emitting element was driven at a constant current at an initial luminance of 300 cd / m ² , the light emission lifetime (half life until the luminance was reduced by half) was 1800 hours.

<Examples 2 to 5>
An organic electroluminescent device was produced in the same manner as in Example 1 except that compounds having structural formulas shown in Table 6 below were used as the organic material of the light emitting layer 14c in FIG. . Table 6 below also shows the evaluation results.

<Comparative Example 1>
The organic electric field was exactly the same as in Example 1 except that 3-phenylfluoranthene (see JP-A-10-189248) represented by the following structural formula (19) was used as the organic material of the light emitting layer 14c in FIG. A light emitting element was prepared and evaluated in the same manner. The results are shown in Table 6 above.

<Comparative example 2>
An organic electroluminescent device was prepared and evaluated in the same manner as in Example 1 except that 3- (naphthalen-1-yl) fluoranthene represented by the following structural formula (20) was used as the organic material of the light-emitting layer 14c in FIG. Went. The results are shown in Table 6 above.

  From the results shown in Table 6 above, the organic electroluminescent elements of Examples 1 to 5 in which the light emitting layer 14c in the organic layer 14 is configured using the organic light emitting material of the present invention are structural formulas (19) and structural formulas. Compared with the organic electroluminescent elements of Comparative Examples 1 and 2 in which the light emitting layer 14c in the organic layer 14 is formed using the compound (20), the light emission luminance at the constant voltage (6V) drive is comparable. Although the luminous efficiency is comparable, it has been confirmed that the luminous lifetime is greatly improved.

<Example 6>
As the light-emitting layer 14c in FIG. 2, 9,10-di (2-naphthyl) anthracene (ADN) represented by the following structural formula (21) was deposited to form a film with a thickness of 50 nm. At that time, 2,2′-bifluoranthene [Structural Formula (2) in Table 1] produced in Synthesis Example 2 was doped into ADN at a relative film thickness ratio of 5% to form a light emitting layer 14c.

  Subsequently, Alq3 was vapor-deposited with a film thickness of 20 nm as the electron transport layer 14d. When the organic electroluminescent device produced in this way was driven by a direct current voltage, blue coloration was confirmed, and the emission luminance was 1000 cd / m @ 2 at a voltage of 6V. Further, when this light-emitting element was driven at a constant current with an initial luminance of 300 cd / m 2, the light emission lifetime was as shown in Table 7.

<Examples 7 and 8>
The element configuration is the same as that of Example 6 except that the doping concentration of 2,2′-bifluoranthene [Structural Formula (2) in Table 1] with respect to ADN in Example 6 is changed to each concentration described in Table 7 above. Evaluation was performed. The results are shown in Table 7 above.

  From the results shown in Table 7 above, when the light emitting layer 14c is doped with the organic light emitting material of the present invention, the emission luminance (light emission efficiency) is maintained high and more excellent in the range of the doping amount of 20% by volume or less. It was confirmed that the emission lifetime was obtained.

It is sectional drawing which shows the structure of the organic electroluminescent element in embodiment to which this invention is applied. It is sectional drawing which shows one structure of an organic electroluminescent element.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Organic electroluminescent element, 13 ... Anode, 14 ... Organic layer, 15 ... Cathode, 14b ... Hole transport layer, 14c ... Light emitting layer, 14d ... Electron transport layer

Claims (6)

An organic light emitting material for an organic electroluminescent element represented by the following general formula (1).

However, in the general formula (1), A ^{1 to} A ²⁰ are each independently hydrogen, halogen, hydroxyl group, substituted or unsubstituted carbonyl group having 20 or less carbon atoms, substituted or unsubstituted carbon group having 20 or less carbon atoms. Carbonyl ester group, substituted or unsubstituted alkyl group having 20 or less carbon atoms, substituted or unsubstituted alkenyl group having 20 or less carbon atoms, substituted or unsubstituted alkoxyl group having 20 or less carbon atoms, substituted or unsubstituted 30 carbon atoms or less An unsubstituted aryl group, a substituted or unsubstituted heterocyclic group having 30 or less carbon atoms, a cyano group, a nitro group, or a silyl group is shown. The organic light-emitting material according to claim 1.
One or more of A ^{1 to} A ^{20 in} the general formula (1) are substituted with a substituent selected from an alkyl group, an alkenyl group, an alkoxy group, a heterocyclic group, or an aryl group. Organic light emitting material. In an organic electroluminescent element formed by sandwiching an organic layer between an anode and a cathode,
The organic layer is configured using an organic light emitting material represented by the following general formula (1).

However, in the general formula (1), A ^{1 to} A ²⁰ are each independently hydrogen, halogen, hydroxyl group, substituted or unsubstituted carbonyl group having 20 or less carbon atoms, substituted or unsubstituted carbon group having 20 or less carbon atoms. Carbonyl ester group, substituted or unsubstituted alkyl group having 20 or less carbon atoms, substituted or unsubstituted alkenyl group having 20 or less carbon atoms, substituted or unsubstituted alkoxyl group having 20 or less carbon atoms, substituted or unsubstituted 30 carbon atoms or less An unsubstituted aryl group, a substituted or unsubstituted heterocyclic group having 30 or less carbon atoms, a cyano group, a nitro group, or a silyl group is shown. The organic electroluminescent device according to claim 3, wherein
One or more of A ^{1 to} A ^{20 in} the general formula (1) are substituted with a substituent selected from an alkyl group, an alkenyl group, an alkoxy group, a heterocyclic group, or an aryl group. Organic electroluminescent device. The organic electroluminescent device according to claim 3, wherein
The organic electroluminescent element characterized by the said organic layer being equipped with the light emitting layer comprised using the organic luminescent material shown by the said General formula (1). The organic electroluminescent device according to claim 5, wherein
An organic electroluminescent element, wherein the light emitting layer contains an organic light emitting material represented by the general formula (1) at a ratio of 20% by volume or less.

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