JP5371404B2 - Electron transporting material and light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electron transport material usable as a light emitting layer host material and a hole block electron transport material, an electron transport material, etc., for organic and inorganic blue light emitting materials. <P>SOLUTION: The electron transport material is expressed by formula (1), wherein R<SB>1</SB>to R<SB>4</SB>each represent fluorine or a methyl group, R<SB>5</SB>to R<SB>8</SB>each represent hydrogen, fluorine and a group independently selected from a group consisting of a methyl group, and Ar represents a substituted or unsubstituted &le;20C aryl group or heteroaryl group, a group having not larger than two rings connected, or a group comprising one ring into which two rings are condensed. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a novel low molecular weight amorphous electron transport material and a light emitting device.

  Light-emitting devices using organic carrier transport materials include organic electroluminescent (hereinafter abbreviated as organic EL) light-emitting devices using fluorescent and / or phosphorescent organic light-emitting materials, and inorganic materials such as nanoparticle semiconductors and inorganic semiconductor thin films. There is an organic-inorganic hybrid light-emitting element including a light-emitting material in a light-emitting layer and combined with an organic carrier transport material.

  In a typical configuration example of these light emitting elements, a hole injection layer, an electron block hole transport layer, a light emitting layer, a hole block electron transport layer, an electron transport layer, and a cathode are formed in this order on the anode on the substrate. Yes. In addition, there is an element having a reverse configuration in which a cathode is sequentially formed on a substrate.

  Each layer laminated between the anode and the cathode is made of a carrier transport material having a hole and electron transport capability. As the light emitting layer material, a material having high fluorescence or phosphorescence in addition to carrier transportability is used.

  These light emitting elements have a rectifying property and emit light by direct current drive. When a DC voltage is applied to the device, holes are injected from the anode and electrons are injected from the cathode, and the injected holes and electrons are transported to the light emitting layer and recombined to emit light. During AC driving, light is emitted during forward bias.

  Anode material is transparent conductive film such as ITO (indium tin composite oxide), IZO (indium zinc composite oxide), highly conductive semitransparent metal thin film made of gold or platinum, highly conductive conductive polymer film, etc. Is used.

  The general transparent conductive film used for the anode has an ionization energy of about 5 eV, and the blue light-emitting material has many ionization energies of about 6 eV. Therefore, when directly injecting holes from the transparent conductive film into the light-emitting layer. Has an energy gap of about 1 eV.

The hole injection layer is inserted between the anode and the light emitting layer to reduce the energy gap and increase the efficiency of hole injection from the anode to the light emitting layer. The hole injection layer may be used alone or in combination with one or more layers having a thickness of about 0.5 nm to 100 nm on the anode. As the hole injection material, a semiconductor film having an ionization energy of 5 to 7 eV is used. For example, a film formed by vacuum deposition, ion plating, CVD, sputtering, sol-gel method or the like of an inorganic semiconductor such as amorphous silicon, amorphous carbon nitride, titanium oxide, molybdenum oxide, vanadium oxide, tungsten oxide, nickel oxide, or the like. A film of a composite of poly (3,4-ethylenedioxythiophene) and polystyrenesulfonic acid (abbreviated as PEDOT: PSS) whose rate is adjusted to the semiconductor region, a coating film of a polyaniline-based conductive polymer material, or copper Organic semiconductors such as phthalocyanine, oligothiophene, and buckminsterfullerene, and aromatic tertiary amine compounds such as 4,4 ′, 4 ″ -tris (2-naphthylphenylamino) triphenyl-amine (abbreviated as 2-TNATA) It is a vapor deposition film or a coating film. Further, these organic semiconductor materials include 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ, approximately, electron affinity 5.24 eV) and 2- (6- Dicyanomethylene-1,3,4,5,7,8-hexafluoro-6H-phthalene-ylidene) Acceptors such as malononitrile and Lewis acids such as tetraphenylantimony bromide and FeCl ₃ are doped to reduce resistance. Examples include membranes.

  In addition, a material having an electron affinity between the ionization energy of the anode and the light emitting layer, such as hexadecafluorocopper phthalocyanine having an electron affinity of about 5.4 eV, can be used as the hole injection material.

  In addition, an electron-withdrawing plasma polymerized film such as trifluoromethane is laminated on the transparent conductive film very thinly with a thickness on the order of nm, or the surface of the transparent conductive film is treated with a fluorine-based silane coupling agent or the like. The ionization energy on the surface of the transparent conductive film can be increased to form a hole injection layer.

  The electron blocking hole transport layer is provided with a thickness of about 5 to 30 nm between the hole injection layer and the light emitting layer, and promotes hole transport from the anode to the light emitting layer and leaks electrons injected into the light emitting layer to the anode. It is provided to prevent this. The electron block hole transport material has a HOMO (maximum occupied orbital) level that is higher than the ionization energy of the hole injection layer and lower than the ionization energy of the light emitting layer, and has a LUMO (minimum) that is higher than the electron affinity of the light emitting layer. Low molecular or high-molecular aromatic tertiary amine-based materials having an empty orbital level are mainly used.

  Further, when a phosphorescent material is used for the light emitting layer, a wide energy gap material having a lowest excited triplet level larger than the lowest excited triplet level of the phosphorescent material in order to prevent quenching by the electron block hole transport material. Is required.

  In the light emitting layer of the organic EL light emitting element, a film containing a fluorescent or phosphorescent light emitting material is formed with a thickness of about 5 to 100 nm. The light emitting layer may be formed of a single material, or the host material may be doped with a light emitting material. Usually, in order to prevent concentration quenching and excimer light emission of the light emitting material, the host material is often doped. As the light emitting material, various known low molecular and high molecular fluorescent light emitting materials such as fluorescent anthracene derivatives, benzoanthracene derivatives, styryl derivatives, carbazole derivatives, polyfluorene copolymers, polyphenoxazine copolymers, etc. Phosphorescent materials made of phosphorescent complexes containing heavy atoms such as phosphorescent iridium complexes and platinum complexes, etc., materials having various EL emission colors such as red, blue, green, white, etc. alone or light emitting materials Used in a host material that has a larger energy gap and does not absorb EL emission from the light emitting material.

  As the host material, it is preferable to use an ambipolar material having an energy gap larger than that of the light emitting material, an ionization energy equal to or higher than that, and an electron affinity equal to or lower than that of the light emitting material. It is also possible to use a block hole transport material or a hole block electron transport material.

In an organic-inorganic hybrid type light emitting device in which an organic carrier transport material and an inorganic light emitting layer are combined, or an organic light emitting layer host material includes an inorganic light emitting material, CdS, ZnSe, ZnS, ZnO, CdO, In ₂ O ₃ , A phosphor made of a thin film, fine particles or nanorods based on an inorganic semiconductor such as SnO ₂ is used alone or in combination with an organic carrier transport material for the light emitting layer. In the inorganic semiconductor, a material that forms a light emitting center such as Mn, Tb, or Eu, or a donor or acceptor level such as Ag, Cu, Al, Ga, Cl, or As is added as necessary.

  A blue light-emitting material with good color purity requires a gap between the HOMO energy level (ionization energy) and the LUMO energy level (electron affinity) of about 3 eV or more.

  As an example of an inorganic semiconductor quantum dot light-emitting material developed in recent years, ZnS is epitaxially grown around a core made of semiconductor nanoparticles having a diameter of about 2 to 6 nm of CdSe to form a shell for exciton confinement. Furthermore, there is a material whose surface is modified with a chain molecule such as trioctylphosphine oxide so that it can be dispersed in an organic solvent, and a luminescence quantum yield of about 85% has been reported (Non-Patent Documents 1 to 5).

  The organic electron block hole transporting material film spin-coated with quantum dots is phase-separated according to the concentration of the mixed, and one or two quantum dot layers are formed on the film surface. Thereafter, an organic-inorganic hybrid light emitting device is formed by laminating a light emitting layer and a hole blocking electron transport layer.

  The energy of excitons generated in the organic electron block hole transport layer, the organic light emitting layer, or the hole block electron transport layer is absorbed by the quantum dots, and light emission from the core of the quantum dots can be obtained.

  The hole-blocking electron transport layer has a hole transport capability that is stronger than the electron transport capability of the light-emitting layer, and prevents leakage of holes to the cathode and absorption of exciton energy by the cathode when there is a light-emitting region near the cathode side. In order to increase the luminous efficiency, it is provided with a thickness of about 5 to 50 nm on the cathode side in contact with the light emitting layer.

  A hole block electron transport material for a light emitting device has an ionization energy of at least 0.3 eV or more, preferably 0.7 eV or more larger than that of the light emitting material, and a large energy gap of 3.1 eV or more that does not absorb visible light emission from the light emitting layer. There is a need for a material having

  Therefore, since the ionization energy of a normal blue light emitting material is on the order of 6 eV, an electron transport material having a large ionization energy of 7 eV or more has been demanded as a hole block electron transport material for blue light emitting elements.

Conventionally, as a hole block electron transport material, bathophenanthroline, bathocuproin,
2,2 ′, 2 ″-(1,3,5-benzenetriyl) -tris (1-phenyl-1-H-benzimidazole) (abbreviated as TPBI) or triazine derivative (Patent Documents 1 to 3) Nitrogen-containing heterocyclic compounds such as are used. However, these materials often have a planar molecular structure, and the deposited film is easily crystallized, resulting in insufficient stability. In addition, since it is easy to crystallize in a solution, there are many cases where wet film formation cannot be performed. Therefore, a highly amorphous electron transport material that can form a smooth film not only by vacuum deposition but also when a wet film formation method is applied, and a material having a high heat resistance with a glass transition temperature of 150 ° C. or higher. It has been demanded.

  Patent Documents 1 to 3 describe that each of two phenylene groups between triazine rings may have one methyl group, aliphatic group, halogen, or cyano group substituent. Specifically, although described in detail in the best mode for carrying out the invention described later, only one example of the number of methyl substituents on each phenylene ring is described, and the phenylene ring faces are not necessarily There is a problem in that a large energy gap in the ultraviolet region cannot be obtained because the conjugation spreads between the two triazine rings because they cannot be orthogonal.

  ZnO-based or ZnS-based n-type semiconductors are often used for the shell layer and the inorganic semiconductor light emitting layer of the core / shell type quantum dot phosphor. The ionization energy of CdSe used for the core of quantum dots is about 6.5 eV, the ZnO layer of the shell is 6.6 eV, and the ZnS layer is 7.0 eV. Therefore, it is used for the host material of the light emitting layer and the hole block electron transport material. The material is preferably a material having an ionization energy of about 7.0 eV. In addition, since the electron affinity values of the ZnO layer and the ZnS layer are both 3.4 eV, the electron affinity value is about 3.4 to 4.0 eV in order to inject electrons from the Al electrode (ionization energy 4.28 eV). These materials are considered desirable for electron injection into quantum dots. However, organic light-emitting layer host materials and hole-blocking electron transport materials having an appropriate energy level and film formability have not been used because they are hardly known.

  The electron transport layer is provided with a thickness of about 1 to 50 nm in order to reduce the energy barrier and resistance of electron transfer from the cathode to the hole block electron transport material.

  Examples of materials used for the electron transport layer include compounds containing one or more nitrogen-containing heterocycles such as oxadiazole ring, triazole ring, triazine ring, quinoline ring, phenanthroline ring, pyrimidine ring, pyridine ring, imidazole ring carbazole ring, etc. And complexes. Specific examples include 1,10-phenanthroline derivatives such as bathocuproine and bathophenanthroline, benzimidazole derivatives such as 1,3,5-tris (N-phenylbenzimidazol-2-yl) benzene (hereinafter abbreviated as TPBI), Metal complexes such as bis (10-benzoquinolinolato) beryllium complex, 8-hydroxyquinoline Al complex, bis (2-methyl-8-quinolinato) -4-phenylphenolate aluminum, 4,4′-biscarbazole biphenyl, etc. Is mentioned.

  In addition, aromatic boron compounds, aromatic silane compounds, aromatic phosphine compounds such as phenyldi (1-pyrenyl) phosphine, and the like are also used. Furthermore, in order to further reduce the resistance thereof, films of these compounds, complexes, and organic metals are doped with an alkali metal or alkaline earth metal such as Cs, Na, Li, or Ba as a donor, thereby increasing the carrier density and reducing the resistance. Resistance is also being done.

  The cathode is usually made of Al or Ag with low resistance and high light reflectance. When forming a light transmissive cathode, a transparent electrode material or the like is laminated on a metal cathode of about 10 nm. An organic light emitting material usually has a material having an electron affinity of about 3 eV, and a low work function material of 3 eV or less is used at the light emitting layer interface for efficient electron injection. Rare earths such as Yb, alkali metals such as Li, Ba, and Cs, alkaline earth metals, and salts and complexes thereof are used at the organic layer interface of the cathode. For this reason, when there is moisture, there is a problem that a local battery is formed and is easily corroded and a non-light-emitting spot is likely to occur.

  In the future, if a blue light-emitting material capable of easily injecting electrons even with a cathode material having a high work function that is relatively stable to moisture will be developed, an anode with a high ionization energy of 6 eV or more and an electron block hole transport material will be used. As the energy gap 3 eV, a blue organic light-emitting material having a large ionization energy of about 7 eV and a large electron affinity of about 4 eV is required. In that case, a material having an electron affinity of about 4 eV is required for the host material of the light emitting layer and the hole blocking electron transport layer. When such a blue light-emitting material, a light-emitting layer host material and a hole-blocking electron transport layer material having an unprecedented large electron affinity are developed, Al (4.28 eV) or Ag (4.26 eV) having an ionization energy of 4 eV or more is developed. Thus, only a relatively stable metal such as can be used for the cathode, and the stability of the EL light emitting device can be expected to be improved.

  In addition, as a mass production technique related to a method for forming each organic film of an EL light-emitting element, a vacuum deposition method having excellent film thickness controllability and uniformity is generally used for a low molecular organic material. In addition, a sublimation transfer method (Non-patent Document 6) that can be applied to a large-area substrate has also been attempted.

  Low molecular organic EL materials for vacuum deposition are molecules with a simple and planar structure due to their low molecular weight, and are easy to crystallize. When used in wet film-forming methods such as spin coating and inkjet, the evaporation of the solution In many cases, crystal growth occurred rapidly during drying, resulting in uneven uneven films.

  However, in recent years, efforts have been made to improve the film-forming properties of low-molecular materials, and displays are also being manufactured by a continuous nozzle printing method with excellent mass productivity (Non-patent Documents 7 and 8). In the future, if low-molecular EL materials with improved solubility in solvents, wet-film formation, heat resistance, etc. are increasing, red, blue, and green low-molecular light-emitting materials will be increased by the wet film-forming method. It is also possible to produce an EL display panel by a method of separately applying to an area substrate.

  Furthermore, if a material that can be purified by vacuum sublimation and has high solubility can be designed, vacuum sublimation is possible in addition to purification by column chromatography, and a material having high purity and excellent characteristics can be obtained. Such materials are not only vacuum-deposited films formed with ordinary low-molecular materials, but also an inkjet method suitable for large-area substrates by dissolving in a solvent alone or mixing with other low-molecular materials or polymer materials. In addition, it can be applied to a printing method excellent in mass productivity on a large area substrate such as a continuous nozzle printing method and a relief printing method, and the range of use of the material can be greatly expanded.

In addition, the laser sublimation transfer donor sheet (Non-patent Document 6), which has been manufactured by the conventional vacuum vapor deposition method, is an ink jet method (Non-patent Documents 9 to 12) excellent in mass productivity, cap coating method, slit coating method, letterpress printing. It is also possible to form and manufacture a film by a coating printing method such as a method (Non-patent Document 13).
Seth Coe, Wing-Keung Woo, Moungi Bawendland Vladlmir Bulovic, Nature, Vol 402, 800 (2002). Sumit Chaudhary, Mihrimah Ozkan and Warren CWChan, Applied physics letters, 84, 2925 (2004). M. Anni, L. Manna, R. Cingolani, D. Valerini, A. Creti and m. Lomascolo, Applied physics letters, 85, 4169 (2004). Yanqin Li, Aurora Rizzo, Marco Mazzeo, Luigi Carbone, Liberato Manna, Roberto Cingolani and Giuseppe Gigli, Applied physics letters, 97, 113501 (2005). Peter T. Kazlas, Jonathan S. Steckel, Marshall Cox, Caroline Roush, Dorai ramprasad, Craig Breen, Mead Misic, Vincent diFilippo, Maria Anc, John Ritter, and Seth Coe-Sullivan, SID07 DIGEST P-176 (2007). Takashi Hirano, Keisuke matsuo, Kokichi Kohinata, Koji Hanawa, Tatsuya Matsumi, Eisuke Matsuda, Ryoko Matsuura, Tadashi Ishibashi, Akihiko Yoshida, and Tatsuya Sasaoka, SID07 DIGEST 53.2 (2007). M. Masuichi, M. Kawagoe, Y. Takamura, H. Adachi, Y, Fujimoto, and M. Ueno, SID05, DIGEST, 30.1 (2005). WFFeehery, SID07 DIGEST, 69.1 (2007). T.FUNAMOTO, Y. Matsueda, O. Yokoyama, A. Tsuda, H. Takeshita, A. Miyashita, SID 02 DIGEST, 27.5L (2002). T. Shimoda, SID 03 DIGEST, 39.1 (2003). David Albertalli, SID 05 DIGEST, 30.3 (2005). Tadashi Gohda, Yuhki Kobayashi, Kiyoshi Okano, Satoshi Inoue, Ken Okamoto, Satoshi Hashimoto, Emi Yamamoto, Haruyuki Morita, Seiichi Mitsui and Mitsuhiro Koden, SID 06 DIGEST, 58.3 (2006). E. Kitazume, K. Takeshita, K. Murata, Y. Qian, Y. Abe, M. Yokoo, K. Oota, T. Taguchi, SID06DIGEST, 41.2 (2006). US Pat. No. 6,057,048 US Pat. No. 6,225,467 US Pat. No. 6,229,012

  The present invention provides an electron transporting material having a wide energy gap that can be suitably used as a light emitting layer host material, a hole block electron transporting material, an electron transporting material and the like for organic and inorganic blue light emitting materials. Objective.

  Furthermore, an object of the present invention is to provide a solid or liquid composition for printing ink containing the compound of the present invention having high solubility in an organic solvent.

  It is another object of the present invention to provide a light-emitting element capable of efficiently emitting blue light with a wide energy gap using an electron transporting material that can be deposited and wet-formed.

  According to one aspect of the present invention, the following formula (1)

(Wherein R ₁ to R ₄ represent fluorine or a methyl group, R ₅ to R ₈ represent a group independently selected from the group consisting of hydrogen, fluorine and methyl group, and Ar represents a carbon number of 20 or less. A substituted or unsubstituted aryl group or heteroaryl group in which two or less independent rings are linked, or a group consisting of one ring in which two rings are fused)
An electron transporting material represented by the following structure is provided:

  According to another aspect of the present invention, there is provided an ink composition comprising at least one electron transport material.

  Furthermore, in a light-emitting element containing an organic or inorganic light-emitting material in at least one layer between opposed electrodes or between an anode and a cathode, at least one layer formed between the opposed electrodes or between the anode and the cathode Is provided with an electron transporting material according to the present invention.

  The novel electron transporting material according to the present invention is a low molecular electron transporting material having a wide energy gap suitable for blue light emitting devices capable of vacuum deposition and wet deposition.

The novel electron transporting material according to the present invention has a structure having a biphenylene group between two triazine rings having a large electron affinity and an electron transporting property, and the substituents R ₁ to R ₈ of the biphenylene group are fluorine or methyl group. A structure substituted with is possible. Electron-withdrawing fluorine has the effect of increasing the value of electron affinity and ionization energy, and the electron-donating methyl group contributes to the effect of reducing these values.

Further, one or more groups of R ₉ to R ₁₈ can be substituted with an electron-withdrawing fluorine, trifluoromethyl group or the like, or substituted with an electron-donating methyl group or methoxy group.

By selecting and combining electron-withdrawing and electron-donating substituents of R ₁ to R ₁₈ , the electron affinity and ionization energy values of the material of the present invention can be easily adjusted according to the energy level of the light emitting material and the cathode. Can do.

For example, a material having a large electron affinity of 4.0 eV or more and a large ionization energy of 7.3 eV or more, such as the compound (A) in which fluorine is selected from the formulas R ₁ to R ₈ can be used. , A light-emitting material having a large ionization energy of about 7 eV can function as a hole-blocking electron transport material.

  In addition, if the electron affinity of the material of the present invention is brought close to the work function of a relatively stable cathode material such as Al, electron injection without including a low work function material such as an alkali metal that easily deteriorates with moisture in the cathode material. Can also be expected to be easily effected.

Further, the novel electron transporting material according to the present invention has four substituents R ₁ to R ₄ , and these are fluorine or methyl groups having a relatively large steric hindrance. Can be orthogonal. Therefore, by deconjugating the biphenylene group, it is possible to obtain a HOMO-LUMO energy gap larger than 3 eV that does not absorb blue light emission, so there is no substantial light absorption in the visible region of 400 nm or more, and the light emitting material Does not adversely affect the light emission.

  In addition, since the compound of the present invention does not emit fluorescence, it does not adversely affect the EL emission spectrum of the light emitting dopant when used in the host material of the light emitting layer or a layer adjacent to the light emitting layer.

  Furthermore, the electron transporting material according to the present invention has an effect of suppressing the crystallinity of the molecule and improving the amorphous property because the molecular structure becomes non-planar because the phenylene ring faces of the biphenylene group between the triazine rings are almost orthogonal. The solubility with respect to an organic solvent and the film-forming property can be improved.

  By having a substituent on the aryl group or heteroaryl group substituted on the triazine ring, the amorphous property and the solubility in an organic solvent can be further improved, and it has the effect of being easily converted into an ink and wet-formed.

  In addition, the electron transporting material of the present invention can be formed by vacuum evaporation when the molecular weight is 1200 or less, more preferably 900 to 1000 and has a structure without a thermal crosslinkable group. It becomes possible to correspond to the process. Purification by distillation or sublimation can be performed, and a high-purity material can be provided, which is useful as an electron transporting material.

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

  According to the invention, the formula (1)

(Wherein R ₁ to R ₄ represent fluorine or a methyl group, R ₅ to R ₈ represent a group independently selected from the group consisting of hydrogen, fluorine and methyl group, and Ar represents a carbon number of 20 or less. A substituted or unsubstituted aryl group or heteroaryl group in which two or less independent rings are linked, or a group consisting of one ring in which two rings are fused)
Is provided.

The electron transporting material according to the present invention has a substituent having a relatively large steric hindrance at the R ₁ to R ₄ positions in the formula (1). Therefore, the phenylene ring faces are orthogonal to each other, and the conjugation does not spread between the two triazine rings. Accordingly, a HOMO-LUMO energy gap larger than 3 eV that does not absorb blue light emission can be obtained, and the material has substantially no absorption in the visible region of 400 nm or more, and the light emitting material having a light emission spectrum in the visible region absorbs light emission. Does not adversely affect.

  Furthermore, by having a substituent on the aryl group or heteroaryl group that replaces the triazine ring, crystallization is inhibited, and it has high amorphousness and high solubility in an organic solvent.

  The compound of the present invention can be synthesized as in the following synthetic reaction formula (a) or the following synthetic reaction formula (b). However, it is not necessarily limited to these examples.

Here, the Ar group, Ar ₁ group, and Ar ₂ group have, as a skeleton, a tolyl group having 6 to 10 carbon atoms, an aryl group such as a phenyl group or a naphthyl group, or a heteroaryl group such as a pyridyl group or a carbazolyl group. The skeleton of the Ar group, Ar ₁ group, and Ar ₂ group includes, as a substituent, fluorine, a methyl group having 1 to 8 carbon atoms, an ethyl group, an isopropyl group, a tertiary butyl group, a hexyl group, a heptyl group, and an octyl group. Alkyl groups such as vinyl groups having 2 to 8 carbon atoms, alkenyl groups such as hexenyl groups and octenyl groups, alkoxy groups such as methoxy groups and oxypentenyl groups, phenyl groups, tolyl groups, fluorophenyl groups, heptyl It may have a substituted phenyl group such as a phenyl group, a substituted aryl group such as a thionylphenyl group, or a substituted heteroaryl group such as a phenylpyridyl group. In addition, the skeleton of Ar group, Ar ₁ group, Ar ₂ group can be converted into alkenyl group having 2 to 8 carbon atoms such as vinyl group, pentenyl group, hexenyl group, octenyl group, pentenyloxy group, hexenyloxy group, octenyloxy group. Heat, light, catalyst, cross-linking agent by substituting with an alkoxy group having a reactive double bond such as a vinyl group, vinyloxy ether group, 1,2,2-trifluorovinyloxy group, an epoxy group or an oxetane group The crosslinkable polymerizability can be imparted. Therefore, it can be insolubilized in an organic solvent.

Specific examples of the substituents R _{1 to} R ₈ are represented by X1 to X5 in Table 1. Specific examples of the substituent Ar are indicated by Y1 to Y38 in Table 2.

The compound of the formula (1) is a biphenyl derivative compound having X1 to X5 in Table 1 as a substituent and a nitrile derivative having an Ar group in Table 2 as a substituent, or a triazine having an Ar ₁ group or an Ar ₂ group as a substituent. They can be synthesized by any combination of reactions using chloride derivatives as raw materials.

中でも、Ｒ₁からＲ₄がフッ素である式（２）

Among them, the formula (2) wherein R ₁ to R ₄ are fluorine

(Wherein R ₅ to R ₈ represent groups independently selected from the group consisting of hydrogen, fluorine and methyl groups, and R ₉ to R ₁₈ represent hydrogen, fluorine, alkyl groups having 1 to 8 carbon atoms and alkoxy groups. indicating group, an alkenyl group having from 2 to 8 carbon atoms, a trifluoromethyl group, and a substituted or unsubstituted phenyl group, a thienyl group, a group selected from the group consisting of a pyridyl group and a carbazolyl group)
An electron transporting material characterized by being represented by the structure:

The compound represented by the formula (2) of the present invention is a compound in which R ₁ to R _{4 in} the formula (1) are substituted with fluorine, and not only non-planarizing the biphenylene group due to its steric hindrance but also its electron Due to the attraction, the electron affinity can be further increased than in the case of the methyl group, and when the LUMO level is lowered and the hole blocking electron transport layer is used, the hole blocking ability can be increased.

At least one or more of the substitution positions R ₉ to R _{18 of} each phenyl group substituting the triazine ring in the compound of the formula (2) is from 1 carbon number such as methyl group, isopropyl group, tertiary butyl group, octyl group and the like. By substituting with an alkyl group of 8 or an alkoxy group such as methoxy, the amorphous nature and solubility in an organic solvent can be improved, and ink can be formed at a concentration of 1 wt% or more.

In addition, if one or more of the substituents R ₉ to R ₁₈ are substituted with an electron-withdrawing fluorine or trifluoromethyl group, the ionization energy and electron affinity can be further increased. Can be adjusted.

  Moreover, Formula (A)

The electron transporting material represented by the formula (2) is a compound in which the substituents of R ₅ to R _{8 in} the formula (2) are further substituted with fluorine, and can have a large electron affinity of 4 eV. Further, since the compound of the formula (A) can be dissolved at a high concentration of about 0.1 g in 1 ml of toluene, the use amount of the organic solvent having a large environmental load is reduced by using the high concentration ink for printing. It is also possible.

  The electron transporting material according to the present invention is a blue light emitting material having a large energy gap of 3.1 eV or more having substantially no light absorption in the visible region of 400 nm or more and an ionization energy of about 6 eV due to limitations on the types and number of substituents. It is an electron transporting material having a large ionization energy of about 7 eV or more that works effectively on the material.

  Here, the following formula (3) similar to the electron transporting material represented by the formula (1) of the present invention and a compound having a structure of, for example, the formula (F) are described in Patent Documents 1 to 3.

However, since these compounds do not have substituents at all the positions corresponding to the R _{1 to} R ₄ positions of the formula (1) of the present invention, the phenylene ring faces cannot always be orthogonal to each other, and two phenylene groups rotate. The resulting surface is planarized and conjugation can spread between the two triazine rings. Therefore, an energy gap that absorbs a part of the short wavelength component near 400 nm in the emission spectrum of the blue light emitting element is obtained, and the ultraviolet light having no absorption of the entire blue emission spectrum like the electron transporting material of the formula (1) according to the present invention. It is difficult to obtain a material having a large energy gap in the region.

  The ink composition of the present invention contains an electron transporting material represented by the formula (1) in an organic solvent. The electron transporting material of the formula (1) of the present invention is inhibited from crystallization by a substituent of the triazine ring, and has high amorphousness and high solubility in an organic solvent. The ink composition of the present invention may contain at least one other kind of carrier transporting material and light emitting material depending on the application.

  The light emitting device of the present invention is a light emitting device containing an organic or inorganic light emitting material in at least one layer between opposed electrodes or between an anode and a cathode, and formed between the opposed electrodes or between the anode and the cathode. At least one layer formed contains the electron transporting material of the present invention represented by the formula (1). For example, the electron transporting material of the present invention can be used as a host material in the light emitting layer, a material in the hole block electron transporting layer, and an electron transporting material in the electron transporting layer.

In the light-emitting element of the present invention, the organic light-emitting material described during the production of the organic EL light-emitting element described below can be used as the light-emitting material. CdS, ZnSe, ZnS, ZnO,
An inorganic semiconductor thin film based on an inorganic semiconductor such as CdO, In ₂ O ₃ , SnO ₂ , TiO ₂ , or SiC, or an inorganic semiconductor fine particle having a diameter of 10 nm or less, or an inorganic semiconductor having a diameter of several nm to several hundred nm, for example. Inorganic light emitting materials such as nanorods and nanowires can also be included. As these inorganic materials, an inorganic semiconductor quantum dot light-emitting material that can be applied as described in the background art can be preferably used. For example, ZnS is epitaxially grown around a core (nucleus) made of semiconductor nanoparticles having a diameter of about 2 to 6 nm of CdSe to form a shell for exciton confinement, and the surface is a chain molecule such as trioctylphosphine oxide. It is a modified material that can be dispersed in an organic solvent.

  Subsequently, a case where an organic EL light emitting device is mainly manufactured using the electron transporting material of the present invention will be described with reference to FIGS. 1 to 4.

  In the organic EL device of the present invention, the compound of the present invention represented by the formula (1) contains the organic light emitting material in at least one layer between opposing electrodes or between the anode and the cathode. Although it can be used for at least one layer formed between the opposing electrodes or between the anode and the cathode, more preferably, the host material of the light-emitting layer, or the hole-blocking electron transport layer, or at least one of the electron transport layers Can be used for layers.

  FIG. 1 is a cross-sectional view of an organic EL light emitting device according to one embodiment of the present invention. In FIG. 1, an anode 2 made of a transparent electrode or the like is formed on a substrate 1, and a hole injection layer 3, a light emitting layer 4, and a cathode 5 are sequentially stacked on the anode 2 to form an organic EL light emitting device. It is configured. The anode 2 is electrically connected to the power source 7 via the wiring 6, the cathode 5 is connected to the terminal portion 8 formed on the substrate, and is further electrically connected to the power source 7 via the wiring 9. Optionally, a passivation layer 13 may be provided on the cathode 5.

  FIG. 2 is a sectional view of an organic EL light emitting device according to another embodiment of the present invention. In the organic EL light emitting device shown in FIG. 2, an electron block hole transport layer 10 is laminated on the hole injection layer 3 of the organic thin film EL device shown in FIG.

  FIG. 3 shows a cross-sectional view of an organic EL light emitting device according to another embodiment of the present invention. In the organic EL light emitting device shown in FIG. 3, a hole block electron transport layer 11 is laminated on the light emitting layer 4 of the organic thin film EL device shown in FIG.

  Further, the organic EL light emitting device shown in FIG. 4 has a structure in which an electron transport layer 12 is formed between the light emitting layer 4 and the cathode 5 of the device shown in FIG.

  The organic thin film EL device of the present invention shown in FIGS. 1 to 4 mainly includes the host material in the organic light emitting layer, the hole block electron transport layer, or the electron transport of the present invention of the formula (1) in the electron transport layer. Contains functional materials.

  Hereinafter, the organic thin film EL element of the present invention will be described in more detail.

  As a kind of board | substrate used with the organic electroluminescent light emitting element of this invention, metal foil, a semiconductor, and an insulating transparent board | substrate can be used.

  Examples of the material constituting the substrate made of metal foil include copper, aluminum, invar, stainless, and titanium foils, iron alloy-based or zirconium alloy-based substrates such as amorphous metal tapes. it can. An organic insulating film such as polyimide or a nitride film such as aluminum nitride, an oxide film such as alumina, an oxynitride film such as silicon oxynitride, or an inorganic glass film such as an inorganic glass film is applied to this substrate, sputtering, chemical vapor By forming by a method such as deposition or anodic oxidation, the substrate is flexible and can have a high water vapor barrier property, oxygen barrier property, and high thermal conductivity.

  Examples of the substrate made of a semiconductor include a single crystal wafer substrate such as silicon and silicon carbide. The p-type and n-type semiconductor layers can be formed epitaxially to form a fine CMOS drive circuit or the like and used for a micro display or the like.

  Examples of the insulating transparent substrate include glass, a plastic film such as polyethersulfone and polyethylene naphthalate, and a transparent insulating substrate such as a fiber reinforced epoxy resin.

  Hereinafter, the case where the organic EL light-emitting elements are sequentially manufactured from the anode side using the insulating transparent substrate 1 will be described in more detail. Here, the insulating transparent substrate 1 from which light is extracted may be colored in order to adjust color contrast and improve resistance. Alternatively, a circular polarizing filter, a multilayer antireflection filter, an ultraviolet absorption filter, an RGB color filter, a fluorescence wavelength conversion filter, a silica coating layer, and the like may be provided on the insulating transparent substrate 1.

  Next, the anode 2 is formed on the substrate 1. As the anode 2, a transparent electrode or the like can be used when light is extracted from the substrate side.

  Examples of transparent electrodes include films made of zinc oxide amorphous or microcrystalline transparent oxide conductors doped with ITO or aluminum, acceptor doped polyaniline, polypyrrole, polythiophene, etc. Examples thereof include molecular films. The transparent electrode is used when viewing the display from the substrate side. A transparent conductive film having a visible light transmittance of 80% or more and a surface resistance of about 1 to 50 Ω / □ is usually used as the transparent electrode, but it is desirable to use a lower resistance film for simple matrix driving. In order to make a film having a lower resistance, a layer having a thickness of about 10 nm made of an alloy of silver and copper or the like is formed of an amorphous material containing ITO, indium zinc composite oxide, titanium oxide, tin oxide, or the like as a component. It can also be sandwiched between microcrystalline transparent conductive films and used as a transparent electrode of 1Ω / □ or less. These transparent electrodes are formed on the insulating transparent substrate by a method such as vacuum vapor deposition or sputtering. In addition, a metal bus line made of a metal mainly composed of Cr, Cu, Al, Ag, or the like can be provided in contact with the transparent electrode line to reduce the resistance.

  In the case where the anode 2 is a top emission structure element that extracts light from the cathode side, a black electrode having a high display contrast or a light reflective electrode that can increase the light emission efficiency can also be used.

  Examples of black electrode materials include carbon-based films such as graphite, platinum black films, and metal electrodes with a black metal oxide film with oxygen deficient in the stoichiometric ratio such as molybdenum, tungsten, and copper. Can be mentioned.

  As an example of the reflective electrode, a light reflective metal film such as aluminum, chromium, nickel, platinum or the like is formed on a transparent substrate such as glass or an opaque substrate such as a semiconductor wafer, and ITO (indium) is further formed on the metal film. A transparent conductive film such as tin composite oxide) or IZO (indium zinc composite oxide), or a metal oxide semiconductor film such as tungsten oxide or molybdenum oxide can be used.

  Next, one or more hole injection layers 3 are stacked on the anode 2 to promote hole injection. As the material used for the hole injection layer 3 of the organic EL light emitting device of the present invention, the materials described in the background art can be used with a thickness of about 0.5 to 100 nm. Next, when the electron block hole transport layer 10 or the organic light emitting layer 4 to be laminated is formed by vapor deposition, a known hole injection material soluble in an organic solvent can be used. In the case where the organic light emitting layer 4 is formed by a wet method using an aromatic solvent such as a printing method, vanadium oxide, molybdenum oxide, tungsten oxide, titanium oxide, selenium which is hardly soluble in an aromatic solvent such as toluene used for printing. Spin coating, dip coating, roll coating, blade coating, cap coating, ink jet printing, letterpress printing, nozzle printing by dissolving in inorganic semiconductor materials such as silicon, organic vapor deposition materials insoluble in toluene, or organic solvents such as toluene It is desirable to use a polymer material that can be crosslinked and insolubilized by light or heat after coating by a method such as a method.

  Deposition materials that are hardly soluble in aromatic solvents such as toluene include blue copper phthalocyanine derivatives, green chlorinated and brominated copper phthalocyanine derivatives, red quinacridone derivatives, etc. By using it as a hole injection layer, it is possible to provide a color filter function and correct the EL emission spectrum.

  Examples of polymer materials that can be insolubilized by light or heat after coating include HT-1 (ionization energy 5.8 eV, electron affinity 2.5 eV) manufactured by Kanto Chemical Co., Ltd. represented by the formula (G) Can be mentioned. These may be a polymer having a reactive double bond that crosslinks with light or heat and an average molecular weight of about 10,000 to 500,000 including a hole-transporting aromatic tertiary amine.

(In the formula, n is an integer representing the degree of polymerization).

  Further, these organic hole injecting and transporting layers can be used by reducing the resistance by mixing about 1 to 10 wt% of the acceptor material such as F4-TCNQ described above.

  Next, the electron block hole transport layer 10 is laminated as necessary. The electron block hole transport layer 10 is laminated with a thickness of about 5 to 50 nm in order to suppress the electrons in the light emitting layer from passing to the anode side and increase the light emission efficiency. However, when the hole-electron recombination region in the light emitting layer is from the cathode side, it can be omitted. Conversely, when the recombination region of holes and electrons is from the anode side, holes and electrons are likely to accumulate at the interface between the light emitting layer and the electron block hole transport layer. When holes and electrons accumulate at the interface, a high electric field is applied to molecules near the interface, causing polarization, or causing an irreversible degradation reaction. Therefore, it is desirable to select a material having a small difference in ionization energy between the electron block hole transport layer and the light emitting layer so that holes are smoothly injected into the light emitting layer and holes are not accumulated at the interface.

  The material used for the electron block hole transport layer 10 may be an aromatic tertiary amine low molecular weight hole material or a polymer material having the energy level relationship described in the background art.

  Examples of aromatic tertiary amine low molecular weight hole materials include N, N′-di (1-naphthyl) -N, N′-diphenyl-1,1′-biphenyl-4,4′-diamine ( Ionization energy 5.4 eV, electron affinity 2.3 eV), 4,4 ′, 4 ″ -tris (N-carbazolyl) triphenylamine (TCTA, abbreviated, ionization energy 5.7 eV, electron affinity 2.4 eV) and N , N′-carbazolyl-3,5-benzene (abbreviated as m-CP, ionization energy 6.1 eV, electron affinity 2.4 eV) and the like. These materials can be formed by vacuum deposition.

  When film formation of the light emitting layer in the subsequent process is performed by wet film formation such as a printing method, it is desirable to use a crosslinking material such as a polymer of the formula (G) insolubilized in the solvent of the light emitting layer. .

Next, the light emitting layer 4 is laminated on the hole injection layer or the electron block hole transport layer.
The electron transporting material of the formula (1) of the present invention has a wet film-forming property alone and does not substantially absorb visible light. it can. Specifically, materials in any combination of X1 to X5 in Table 1 and Y1 to Y45 in Table 2 can be used.

  More specifically, the compound of the formula (A) whose synthesis method is described in the examples by the combination of X1 of Table 1 and Y1 of Table 2, the compound of the formula (H) that can be similarly synthesized by the combination of X2 and Y1, etc. Can be mentioned.

  A light emitting dopant made of a low-molecular or high-molecular fluorescent material or phosphorescent material that emits light in an emission wavelength region such as blue, green, red, white, or infrared is added to these host materials at about 0.5 to 50 wt%. The light emitting layer 4 can also be mixed with the electron transporting material of the formula (1) of the present invention at a concentration.

  At that time, when the emission dopant is associative to form excimer emission and the emission wavelength is increased, the emission dopant is mixed at a concentration of about 0.5 to 5 wt%. When excimer light emission is not formed even at a high concentration, a light emitting dopant can be mixed at a concentration of about 5 to 50 wt%. However, when the film is easily crystallized at a high concentration, it is added at a concentration of 25 wt% or less. It is desirable for carrier transfer from the host material to the dopant that both the LUMO and HOMO energy levels of the luminescent dopant are within the range of the LUMO energy level of the host material to the value of the HOMO energy level. However, if one level of HOMO or LUMO does not fit, carrier injection into the light emitting layer and carrier movement within the light emitting layer by carrier hopping between the dopants are possible, at least 5 wt% or more, The light emitting dopant is preferably mixed at a concentration of 10 wt% or more. Alternatively, it is desirable to mix other small and high molecular carrier transport materials having HOMO or LUMO energy levels that allow carrier movement.

  In addition, in order to adjust the carrier balance and the viscosity of the ink, other low molecular hole transport materials and polymer holes such as poly (N- (vinylvinyl) carbazole) and poly (N- (4-vinylphenyl) carbazole) A light emitting layer may be formed by mixing a transport material and other electron transport materials.

  Below, examples of blue, green, red and yellow light emitting materials that can be doped into the electron transporting material of the present invention in the light emitting layer are the low molecular compounds of formula (I) to formula (Y), formula (Z) However, the present invention is not limited to these colors and materials.

  Examples of blue-emitting dopant compounds include formula (I), anthracene derivative compounds of formula (J), and perylene derivative compounds of formula (K), and phosphorescent Ir complexes of formula (L) and formula (M). It is done.

(Wherein R represents hydrogen, an alkyl group having 4 or less carbon atoms, an alkoxy group, or a trifluoromethyl group).

(Wherein R represents hydrogen, an alkyl group having 4 or less carbon atoms, an alkoxy group, or a trifluoromethyl group).

(Wherein R represents an alkyl group having 4 or less carbon atoms, an alkoxy group, or a trifluoromethyl group).

  Examples of green luminescent dopant compounds include quinacridone derivatives of formula (N), benzoanthracene derivatives of formula (O), formula (P), formula (Q) and formula (R), phosphorescent Ir complexes of formula (S) Etc.

(Wherein R represents hydrogen, an alkyl group having 4 or less carbon atoms, an alkoxy group, or a trifluoromethyl group).

(Wherein R represents hydrogen, an alkyl group having 4 or less carbon atoms, an alkoxy group, or a trifluoromethyl group).

  Examples of red light emitting dopants include 9,14-diphenyl-benz [5,6] indeno [1,2,3-cd] perylene, whose structure is shown in formula (T), in formula (U) and formula (V). A phosphorescent Ir complex showing the structure can be given.

(Wherein acac represents an acetylacetonate ligand).

(Wherein acac represents an acetylacetonate ligand).

  Examples of yellow luminescent dopant compounds include rubrene of formula (W) and phosphorescent Ir complexes of formula (X) and formula (Y).

(Wherein acac represents an acetylacetonate ligand).

(Wherein acac represents an acetylacetonate ligand).

  In order to obtain a single-layer light emitting layer that emits white light, it is possible to emit white light by energy transfer by adjusting the concentration of blue, green, and red light emitting dopants in the order of blue> green> red. Alternatively, a white light emitting layer can be formed by stacking three layers of a blue light emitting layer, a green light emitting layer, and a red light emitting layer. Furthermore, it is possible to improve the color rendering coefficient by adding a yellow light emitting dopant to the single light emitting layer, and to increase the energy transfer efficiency to the red dopant.

  Moreover, a high molecular material can also be used as a positive hole transport material mixed with the electron transport material of this invention, and a light emission dopant.

  For example, a copolymer of an N-arylcarbazole derivative represented by the formula (Z) manufactured by Kanto Chemical Co., Inc. can be used as the hole transporting polymer blue light emitting dopant.

(Where l and m are integers representing the composition ratio of the monomers, and n is an integer representing the degree of polymerization)
Conversely, the electron-transporting material of the present invention can be used as an electron-transporting dopant to dope other low-molecular and polymer light-emitting materials and light-emitting layer host materials at a concentration of less than 5 to 50 wt%.

  In addition, when an organic host material is doped instead of a quantum dot made of an organic material or an inorganic semiconductor, or when a light-emitting semiconductor thin film is used for a light-emitting layer, an organic-inorganic hybrid EL light-emitting device is manufactured. Can do.

  The light emitting layer 4 can be formed by an appropriate film forming method such as vacuum deposition, laser transfer, continuous nozzle printing, ink jet, slit coating, spin coating, letterpress printing, offset printing, gravure printing, etc., preferably 5 The film is formed to a thickness of ˜100 nm.

  Next, a hole blocking electron transport layer 11 is laminated between the light emitting layer 4 and the cathode 5 as necessary.

  The hole blocking electron transport layer 11 is used as a light emitting layer in order to increase the efficiency of electron injection into the organic light emitting layer 4 and to prevent the leakage of holes to the cathode 5 and the absorption of exciton energy by the cathode 5, thereby increasing the light emitting efficiency. It is laminated on the cathode side in contact. The hole block electron transport layer 11 is laminated with a thickness of about 100 nm or less, preferably about 5 to 50 nm, by a method such as vacuum deposition, laser transfer, or coating printing.

  However, the electron transporting property of the light emitting layer 4 is higher than the hole transporting property, the electron blocking hole transporting layer light emitting layer 10 is provided, and the hole-electron recombination region in the light emitting layer 4 is closer to the anode side. In this case, the hole block electron transport layer 11 can be omitted.

  The material used for the hole-blocking electron transport layer 11 has a small dipole moment, a large electron mobility, a large LUMO state density, and an LUMO energy level (electron affinity) of the LUMO of the light-emitting material or the host material in the light-emitting layer 4. It is preferably between the same level as the energy level (electron affinity) and the Fermi level (work function) of the cathode material. More preferably, in order to prevent accumulation of electrons at the interface with the light emitting layer, it is desirable that the LUMO energy level of the light emitting material or the host material is close.

  Further, the ionization energy of the hole block electron transport layer 11 in contact with the light emitting layer 4 is at least 0.3 eV or more than the ionization energy of the light emitting material and the host material in the light emitting layer 4 and is not formed with the light emitting layer material without forming an exciplex. A material with good film properties is preferred.

  The hole-blocking electron transport layer 11 includes an electron transport material of the formula (1) such as the formula (A) or the formula (H) of the present invention, tris (2,4,6-trimethyl-3- (pyridyl-). Organic boron compounds such as 3-yl) phenyl) borane can be used.

  Further, when the light emitting layer 4 is configured by doping a hole transporting dopant in a high concentration in an electron transporting host material, and the hopping movement between the dopants is possible in the light emitting layer 4, the electron transporting property of the light emitting layer Only the host material can be laminated on the light emitting layer 4 and used as a hole block electron transport material. In this case, it is desirable to use a host material whose ionization energy of the host material of the light emitting layer is at least 0.5 eV or more, more preferably 0.7 eV or more larger than that of the doped light emitting material.

  Next, the electron transport layer 12 is laminated with a thickness of 1 to 50 nm on the hole block electron transport layer 11 as necessary.

  The electron transport layer 12 is provided for the purpose of reducing the driving voltage and increasing the film thickness of the organic layer to make it difficult to cause defects. As the electron transport layer material, it is desirable to use a material whose electron affinity is between the electron affinity of the hole block electron transport material and the ionization energy of the cathode.

  Examples of the material used for the electron transport layer 12 include the electron transport material of the formula (1) of the present invention, bathocuproine, bathophenanthroline, phenyldi (1-pyrenyl) phosphine, bis (10-benzoquinolinolato) beryllium complex, 8 -Hydroxyquinoline Al complex, imidazole derivatives such as 2,2 ′, 2 ″-(1,3,5-phenylene) -tris (1-phenyl-1H-benzimidazole), 1,3-bis [2- ( Bipyridine derivatives such as 2,2′-bipyridin-6-yl) -1,3,4-oxadiazo-5-yl] benzene, tris (2,4,6-trimethyl-3- (pyridyl-3-yl) phenyl ) Organic boron compounds such as borane. In addition, it is more preferable to use a film in which an alkali metal or alkaline earth metal donor material such as Cs, Na, Li, or Ba is doped into these materials by co-evaporation to increase the carrier density and lower resistance.

  Subsequently, the cathode 5 is formed directly on the light emitting layer 4. When the hole block electron transport layer 11 and the electron transport layer 12 are laminated on the light emitting layer 4, the cathode 5 is formed on the hole block electron transport layer 11 or the electron transport layer 12.

  The cathode 5 of the EL light emitting element desirably has an interface having an ionization energy smaller than the electron affinity of the light emitting layer 4, the hole blocking electron transport layer 11, or the electron transport layer 12 in contact with the cathode 5. When the low-resistance electron transport layer 12 doped with an alkali metal or alkaline earth metal donor material is not provided, a cathode surface with a high workability and a low work function with an ionization energy of 3.2 eV or less is formed. To do.

  As a low work function cathode surface, a low work function metal element such as an alkali metal such as Li, Na, K and Cs, an alkaline earth metal composed of Mg, Ca, Sr and Ba, and a rare earth metal such as Yb is one atomic layer or more. A stable Al or Ag film is formed thereon with a thickness of 100 nm to 300 nm.

Although rare earth Yb has a low work function of 2.6 eV, it is preferable as a cathode material because it is more stable to moisture than alkali metals and alkaline earth metals.

  The low work function metal element surface is formed by depositing or sputtering a low work function metal element such as a fluoride salt or a compound containing a low work function element such as an oxide or nitride to a thickness of several nanometers or less. And it can also form by partly decomposing | disassembling and adhering. Alternatively, an alloy containing one or more low work function metal elements can be used. However, since these low work function materials are easily corroded by moisture and cause dark spots, strict moisture-proof measures are required.

  In the case of an EL light emitting device using an electron transporting material having an electron affinity of 4 eV represented by the formula (A) of the present invention for the hole block electron transporting layer 11 and the electron transporting layer 12 in contact with the cathode, the cathode 5 is required. The work function value may be about 4 eV, and a relatively stable material in which the ratio of the low work function metal component is reduced can be used.

  The cathode 5 described above can be formed by resistance heating vapor deposition, electron beam vapor deposition, reactive vapor deposition, ion plating, sputtering, or the like depending on the material used.

When the cathode 5 is composed of a multi-component alloy, co-evaporation is performed by using a resistance heating vapor deposition method under a vacuum of the order of 10 ⁻² Pa or less and monitoring from a separate vapor deposition source for each component with a quartz crystal film thickness meter. Form by the method. Alternatively, the alloy material can be formed by flash vapor deposition in small portions. Moreover, it can also form by sputtering method etc. using an alloy target etc.

  In the case where the organic EL element of the present invention is used in a simple matrix drive display and the cathode 5 needs to be formed in a stripe shape as shown in the schematic diagram of FIG. Is deposited in close contact with the substrate. Alternatively, after vapor deposition on the entire surface of the cathode forming portion, it is separated into stripes by the laser ablation method, ion beam etching method, reactive etching method, or the cathode is deposited on the substrate surface on which the reverse tapered resist partition walls are formed in the stripe shape. As a result, the stripe pattern of the cathode 5 can be formed.

  When the thickness of the metal film of the cathode 5 is 5 to 10 nm, visible light can be transmitted and the cathode side can be used as a light emitting display surface.

  In the case of an element configuration in which display is performed from the cathode side, the hole block electron transport layer 11 and the electron transport layer 12 used in the EL light emitting element are substantially transparent at least in the EL light emission wavelength region of the compound of the present invention. Need to be.

  As described above, a structure in which the anode 2, the hole injection layer 3, the electron block hole transport layer 10, the light emitting layer 4, the hole block electron transport layer 11, the electron transport layer 12, and the cathode 5 are stacked in this order from the substrate 1 side. As shown, in the organic EL device of the present invention, a cathode, an electron transport layer, a hole block electron transport layer, a light emitting layer, an electron block hole transport layer, a hole injection layer, and an anode were laminated in order from the substrate side. It may be a structure.

  In the organic EL device of the present invention, it is preferable to form a passivation layer 13 covering the organic layer and the electrode in order to prevent deterioration of the organic layer and the electrode due to moisture and oxygen.

The material used for the passivation layer 13 is not particularly limited as long as the material has high gas barrier properties and water vapor barrier properties, but SiO ₂ , SiO _x , GeO _x , MgO, Al ₂ O ₃ , TiO ₂ , ITO, InZn. _x O _y, and InGa _x Zn _y O _z, and the like of the amorphous oxide (subscript x, y, z represent the composition ratio, composition of these oxides is offset from the stoichiometric ratio Sometimes). Other examples include inorganic compounds such as fluorides such as MgF ₂ , LiF, BaF ₂ , and AlF ₃ , and sulfides such as ZnS. In order to further improve the barrier property, it is desirable to further deposit or sputter deposit a hardly corrosive highly barrier metal such as Al on the passivation layer 13.

  The passivation layer 13 is formed by laminating these materials as a single body or a composite layer by a method such as a vapor deposition method, a reactive vapor deposition method, a CVD method, a sputtering method, and an ion plating method. Is done.

  Further, in order to protect the passivation layer 13 from being damaged, a plastic plate and a plastic film, a metal foil and a plastic laminate film, a metal plate and a metal foil, a glass plate or the like are covered so as to cover the passivation layer 13. Adhesive resin such as low hygroscopic photo-curing adhesive, epoxy adhesive, cross-linked ethylene-vinyl acetate copolymer adhesive sheet, or low-melting glass, etc. Adhere with 15.

  Further, the surface of the passivation layer 13 or the surface of the sealing plate 14 on the light emitting layer 4 side is made of a desiccant such as calcium oxide or barium oxide, or an alkali metal, alkaline earth metal, rare earth, or organic metal. A getter agent layer (not shown) may be formed.

  The organic thin-film EL device of the present invention configured as described above emits light when a direct-current voltage is applied with the hole injection layer 2 side being positive. Even when an AC voltage or a pulse voltage is applied, light is emitted while a positive voltage is applied to the hole injection layer 2 side.

  Further, by arranging the organic thin film EL elements of the present invention two-dimensionally on the substrate 1, a thin display capable of displaying characters and images can be formed.

  Furthermore, as shown in the schematic diagram of FIG. 5, a color display in which sub-pixel lines (26, 27, and 28, respectively) of light emitting layers of three colors of red, blue, and green are formed and light emitting elements of three colors are arranged two-dimensionally. It can be.

  In addition, a color display in which subpixel lines or dots of light emitting elements of four colors of red, blue, green, and white are two-dimensionally arranged, and red, blue, and green corresponding to subpixels on a white light emitting monochrome display are provided. A color display can be produced by laminating color color filters or laminating red, blue, green and transparent color filters.

  In addition, a color conversion with higher light utilization efficiency is achieved by stacking a fluorescent conversion filter that converts blue light-emitting components that emit white light into green pixels and blue and green light-emitting components into red pixels between white light-emitting elements and color filters. Can also be produced.

Example 1
4,4′-bis {2,4-bis (4-tert-butylphenyl) -1,3,5-triazin-6-yl} -2,2 ′, 3,3 ′, 5,5 ′, 6 Of 6,6′-octafluorobiphenyl (Compound A) (Intermediate Synthesis Example 1)
Synthesis of 2,2 ′, 3,3 ′, 5,5 ′, 6,6′-octafluorobiphenyl-4,4′-dicarboxylic acid 2,2 ′, 3,3 ′, 5,5 under argon atmosphere After dissolving 5.0 g (16.8 mmol) of ', 6,6'-octafluorobiphenyl in 55 mL of dehydrated tetrahydrofuran, the mixture was cooled to −70 ° C. or lower. To this, 21 ml (33.6 mmol) of 1.6M n-butyllithium in hexane was added dropwise, and the mixture was aged by stirring at the same temperature for 1 hour. After completion of the anionization, the mixture was stirred for 5 hours while bubbling carbon dioxide at -70 ° C. The mixture was further returned to room temperature and stirred for 12 hours.

  After completion of the reaction, the resulting white gel-like reaction mixture was poured into 6N aqueous hydrochloric acid and extracted with ether. The organic layer was separated and dried over anhydrous sodium sulfate, and then the solvent was distilled off. The obtained powdery crystals were washed with hexane, and 6.0 g (92.2) of 2,2 ′, 3,3 ′, 5,5 ′, 6,6′-octafluorobiphenyl-4,4′-dicarboxylic acid. 7%).

Analysis of the resulting compound was performed directly with a quadrupole mass spectrometer (DI-Ms), and peaks of 386 (M ⁺ ), 342 (M ⁺ -CO ₂ ), and 298 (M ⁺ -CO ₂ ) were observed. The molecular ion peak (M ⁺ ) coincided with the calculated value 386 corresponding to C ₁₄ H ₂ O ₄ F ₈ obtained.

(Intermediate Synthesis Example 2)
Synthesis of 2,2 ′, 3,3 ′, 5,5 ′, 6,6′-octafluorobiphenyl-4,4′-dicarboxylic acid chloride 2,2 ′, 3,3 ′, 5,5 ′, 6 , 6'-octafluorobiphenyl-4,4'-dicarboxylic acid (4.0 g, 10.4 mmol) and thionyl chloride (12 ml) were added with N-dimethylformamide (1-2 ml) until the reaction system became homogeneous. The mixture was stirred at reflux for 14 hours.

  After completion of the reaction, excess thionyl chloride was removed from the reaction mixture, and the resulting oily product was distilled under reduced pressure in a glass tube oven to obtain 2,2 ′, 3,3 ′, 5,5 ′, 6,6′-octa. 4.05 g (92.4%) of fluorobiphenyl-4,4′-dicarboxylic acid chloride was obtained.

Distillation temperature 140 ° C / 0.08mmHg
(Synthesis example)
4,4′-bis {2,4-bis (4-tert-butylphenyl) -1,3,5-triazin-6-yl} -2,2 ′, 3,3 ′, 5,5 ′, 6 , 6′-Octafluorobiphenyl (Compound A) Under an argon atmosphere, 6.39 g (40.2 mmol) of 4-tert-butyl-benzonitryl, 2,2 ′, 3,3 ′, 5,5 ′, A solution consisting of 4.05 g (9.6 mmol) of 6,6′-octafluorobiphenyl-4,4′-dicarboxylic acid chloride and 40 ml of chloroform was cooled to 0 to −5 ° C. To this, 5.72 g (19.1 mmol) of antimony pentachloride was added dropwise and gradually returned to room temperature over 1 hour. Further, the reaction mixture was stirred at reflux for 8 hours, and then the solvent was distilled off from the reaction system under reduced pressure to obtain an oxadianium salt. The oxadianium was pulverized and cooled to 0 ° C., and then 100 ml of 28% aqueous ammonia was added dropwise with stirring, followed by stirring for 12 hours while gradually returning to room temperature.

  After completion of the reaction, the resulting precipitate was collected by filtration with a Kiriyama funnel, washed with water, and then washed with methanol. The obtained white precipitate was suspended in 200 ml of chloroform and then stirred at room temperature for 2 hours to extract the desired product. Further, insoluble matters were removed by filtration, and the filtrate was recovered. After this extraction operation was repeated twice, the obtained filtrate was concentrated to obtain a crude product of yellow foam crystals. Further, this crude product was purified by silica gel column chromatography using a mixed solvent of hexane-methylene chloride (8: 1 to 6: 1) as an eluent, and then recrystallized with acetone to obtain 4,4′-bis { 2,4-bis (4-tert-butylphenyl) -1,3,5-triazin-6-yl} -2,2 ′, 3,3 ′, 5,5 ′, 6,6′-octafluorobiphenyl 1.89 g (yield: 20.0%) was obtained.

The obtained compound had a peak of 985 (M ⁺ +1) by electrospray ionization mass spectrometry (ESI-MS), and coincided with the molecular weight 984 of the target compound C ₅₈ H ₅₂ F ₈ N ₆ .

  The NMR signal is shown below.

¹ H-NMR (400 MHz, d-CDCl ₃ ): δ: 1.41 (s, 36H), 7.60 (d, J = 8.7 Hz, 8H), 8.63 (d, J = 8.7 Hz) , 8H)
¹⁹ F-NMR: (376 MHz, d-CDCl ₃ ): δ: 137 (s, 4F), 140 (s, 4F)
<Absorption spectrum of Compound A>
30 mg of compound A was put into a Bu-6Mo boat manufactured by Bucks Metal Co., Ltd., set in a vacuum vapor deposition apparatus, energized and heated to 385 ° C. under 1E-5 Torr, and deposited on a quartz plate at a thickness of about 59 nm, thereby achieving smoothness. A transparent amorphous film was obtained. FIG. 6 shows the result of measuring the absorption spectrum of this film using a UV-3600 spectrophotometer manufactured by Shimadzu Corporation. There was no absorption of visible light at an absorption edge wavelength of 375 nm (3.31 eV).

<Thermal analysis>
The glass transition temperature (Tg) and melting point (Tm) of Compound A were measured with EXSTAR6000 series DSC6220 manufactured by Seiko Denshi Kogyo. The temperature was raised at 20 ° C./min, and Tm was 350 ° C. to 364 ° C. (peak 365 ° C.). The Tg was 177 ° C. (start of transition) to 192 ° C. (end of transition).

<Solubility>
Compound A was easily dissolved in 1 ml of toluene at room temperature to a concentration of 0.1 g to form an ink.

<Wet film formability>
A transparent and smooth film was obtained by dissolving in toluene at a concentration of 1 wt% and capable of spin coating.

<Measurement of energy level of Compound A>
20 mg of Compound A was dissolved in 1 ml of toluene, spin-coated on ITO transparent electrode glass at 1000 rpm, and the ionization energy was measured with an ionization potential measurement device manufactured by Sumitomo Heavy Industries Advanced Machinery Co. As a result, it was 7.33 eV.

  The electron affinity was 4.02 eV by subtracting the absorption edge energy obtained from the absorption spectrum.

Example 2 Production Example of EL Element Formed by Vapor Deposition Using Compound A as Light-Emitting Layer Host and Hole Block Electron Transport Layer An ITO film having a thickness of 150 nm was formed on a glass substrate 1 having a thickness of 0.7 mm by a magnetron sputtering method. A film is formed as anode 2. Wet etching was performed by a conventional method to pattern the ITO film. The substrate was ultrasonically washed with an alkaline detergent, then further washed with pure water, dried and subjected to ultraviolet cleaning.

Subsequently, MoO ₃ was formed on the ITO film by magnetron sputtering to form a first hole injection transport layer 3 having a thickness of 1 nm.

Next, an ink was prepared by mixing 5 wt% of F4-TCNQ with HT-1 represented by the formula (G) on this MoO ₃ hole injection layer and dissolving about 1 wt% in toluene. This ink was applied to the light emitting portion by a relief printing method to form a film having a thickness of 10 nm. Thereafter, irradiation with 365 nm ultraviolet rays was performed for 30 seconds in a nitrogen atmosphere to crosslink and laminate a toluene-insoluble second hole injection layer 3.

  Further, on the second hole injection layer 3, an ink obtained by dissolving about 1 wt% of HT-1 ink in toluene was applied to the light emitting portion by a relief printing method and laminated to a thickness of 20 nm, and then at 200 ° C. for 30 seconds in a nitrogen atmosphere. Crosslinking was performed by irradiation with 365 nm ultraviolet light to form a toluene-insoluble electron block hole transport layer 10.

  Next, the compound of formula (H) and the phosphorescent blue light-emitting Ir complex (abbreviated as “Firpic”) represented by formula (M) were co-deposited at a vacuum deposition rate of 2 nm / s and 0.2 nm / s, respectively, to a thickness of 70 nm. The light emitting layer 4 was laminated.

  Subsequently, only the compound of the formula (H) was vacuum-deposited with a thickness of 10 nm, and the hole block electron transport layer 11 was laminated.

  Further, the compound (A) and Yb were vacuum-deposited at a deposition rate ratio of 10: 1 to a thickness of 10 nm, and the electron transport layer 12 was laminated.

  Finally, Yb was vacuum-deposited with a thickness of 0.5 nm, Al was vacuum-deposited with a thickness of 200 nm, and the cathode 5 was laminated.

  When a DC voltage of 12 V is applied to this light emitting element, blue EL light emission can be obtained.

Example 3 Example of Fabrication of Device with Light-Emitting Layer Formed by Coating Method After forming up to the electron block hole transport layer 10 in the same manner as in Example 2, a Ferpic represented by the formula (M) in the compound of the formula (A) Was mixed at a concentration of 8 mol%, and an ink dissolved in toluene at a concentration of about 2 wt% was formed into a film having a thickness of 80 nm by a spin coating method.

  Next, only the compound of the formula (A) was vacuum-deposited with a thickness of 10 nm, and the hole block electron transport layer 11 was laminated.

  Subsequently, the compound (A) and Yb were vacuum-deposited at a deposition rate ratio of 10: 1 to a thickness of 10 nm, and the electron transport layer 12 was laminated.

  Finally, Yb was vacuum-deposited with a thickness of 0.5 nm, Al was vacuum-deposited with a thickness of 200 nm, and the cathode 5 was laminated.

  When a DC voltage of 12 V is applied to this light emitting element, blue EL light emission can be obtained.

Example 4 Example of Fabrication of Organic-Inorganic Composite EL Light-Emitting Element Using Quantum Dots After forming up to the electron block hole transport layer 10 in the same manner as in Example 2, the compound (A) and 2 nm of CdSe are used as the core and ZnS is formed. A chloroform solution in which a quantum dot in a shell and a blue light-emitting colloidal particle capped with trioctylphosphine oxide and trioctylphosphine are mixed at a weight ratio of 1: 5 is laminated as a light-emitting layer 4 with a thickness of 80 nm by an ink jet method. Annealed at 300 ° C.

  Next, only the compound of the formula (A) was vacuum-deposited with a thickness of 10 nm, and the hole block electron transport layer 11 was laminated.

  Finally, Yb was vacuum-deposited with a thickness of 1 nm, Al was vacuum-deposited with a thickness of 200 nm, and the cathode 5 was laminated.

  When a DC voltage of 12 V is applied to this light emitting element, blue EL light emission can be obtained.

Example 5 Example of Organic-Inorganic Composite EL Light-Emitting Element Using Inorganic Thin Film Semiconductor After p-type silicon substrate 1 having a thickness of 1 mm was ultrasonically washed with an alkaline detergent, it was further washed with pure water, dried, and washed with ultraviolet rays. went.

Next, a TiO _x film was stacked on the substrate 1 as a hole injection layer 3 by sputtering to a thickness of about 1 nm.

  Subsequently, ZnS containing about 1 mol% of Ag was deposited on the hole injection layer to a thickness of 50 nm by vacuum deposition. Subsequently, ZnS was vacuum-deposited with a thickness of 100 nm. Further, ZnS containing 1 mol% of Al was vacuum-deposited to a thickness of 50 nm, and then annealed in a sulfur atmosphere at 500 ° C. or higher to form a blue light emitting layer 4 made of a ZnS phosphor film. Ag and Al were thermally diffused by annealing and mixed such that the respective concentrations were about 0.05 to 0.1 mol% with respect to Zn. As a result, a blue fluorescent region was formed inside the light emitting layer 4.

  Next, only the compound of the formula (A) was vacuum-deposited with a thickness of 10 nm to form the hole blocking electron transport layer 11.

  Further, the compound of the formula (A) and Yb were vacuum-deposited at a deposition rate ratio of 10: 1 to a thickness of 10 nm to form an electron transport layer 12.

  Finally, Yb is vacuum-deposited to a thickness of 0.5 nm, and Al is vacuum-deposited to a thickness of 200 nm to form a cathode. When a DC voltage of 12 V is applied to this light emitting element, blue EL light emission can be obtained.

Example 6 Example of Light-Emitting Element Using Electron Transport Material of the Present Invention as a Polymer Luminescent Material as a Dopant After forming up to an electron block hole transport layer in the same manner as in Example 2, the compound represented by the formula (H): A hole transporting polymer blue light emitting material of the formula (Z) and tris (2,4,6-trimethyl-3- (pyridyl-3-yl) phenyl) borane as an electron transporting material in a weight ratio of 6: 2: 2. A toluene ink having a solid content of 2 wt% mixed in (1) was formed into a film by a spin coating method, and unnecessary portions were wiped off and dried by heating under vacuum to obtain a light-emitting layer 4 having a thickness of 80 nm.

  Next, only the compound of the formula (H) was vacuum-deposited with a thickness of 10 nm, and the hole block electron transport layer 11 was laminated.

  Subsequently, the compound (A) and Yb were vacuum-deposited at a deposition rate ratio of 10: 1 to a thickness of 10 nm, and the electron transport layer 12 was laminated.

  Finally, Yb was vacuum-deposited with a thickness of 0.5 nm, Al was vacuum-deposited with a thickness of 200 nm, and the cathode 5 was laminated.

  When a DC voltage of 12 V is applied to the light emitting element, long wavelength excimer light emission does not occur and blue EL light emission with high purity can be obtained.

Example 7
A device using a compound having a combination of X3 in Table 1 and Y1 in Table 2 in place of the compound represented by the formula (H) in Example 6 is produced, and similarly, blue light emission is obtained.

Comparative Example 1
In Example 4, a similar device was produced except that the hole block electron transport layer 11 and the electron transport layer 12 were removed. When a DC voltage of 12 V is applied to this element, the current density increases as compared with the element of Example 6, but light emission is hardly obtained.

Comparative Example 2
In Example 5, a similar device was produced except that the hole block electron transport layer 11 and the electron transport layer 12 were removed. When a DC voltage of 12 V is applied to this element, the current density increases as compared with the element of Example 6, but light emission is hardly obtained.

Sectional drawing of the organic EL element which concerns on one Embodiment of this invention. Sectional drawing of the organic EL element which concerns on other embodiment of this invention. Sectional drawing of the organic EL element which concerns on further another embodiment of this invention. Sectional drawing of the organic EL element which concerns on further another embodiment of this invention. The schematic diagram of the organic EL element which concerns on other embodiment of this invention. The absorption spectrum of the compound used with the organic EL element which concerns on one Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Board | substrate 2 ... Anode 3 ... Hole injection layer 4 ... Light emitting layer 5 ... Cathode 6 ... Wiring 7 ... Power supply 8 ... Terminal part 9 ... Wiring 10 ... Electron block hole transport layer 11 ... Hole block electron transport layer 12 ... Electron transport layer 13 ... Passivation layer 14 ... Sealing plate 15 ... Adhesive material 26 ... Resist partition wall 27 ... Red light emitting layer 28 ... Green light emitting layer 29 ... Blue light emitting layer

Claims (7)

An electron transporting material represented by the structure of formula (1):

(Wherein R ₁ to R ₄ represent fluorine or a methyl group, R ₅ to R ₈ represent a group independently selected from the group consisting of hydrogen, fluorine and methyl group, and Ar represents a carbon number of 20 or less. A substituted or unsubstituted aryl group or heteroaryl group in which two or less independent rings are linked, or a group consisting of one ring in which two rings are fused) The electron transporting material according to claim 1, wherein the electron transporting material is represented by a structure of Formula (2):

(Wherein R ₅ to R ₈ represent groups independently selected from the group consisting of hydrogen, fluorine and methyl groups, and R ₉ to R ₁₈ represent hydrogen, fluorine, alkyl groups having 1 to 8 carbon atoms and alkoxy groups. A group selected from the group consisting of a group, an alkenyl group having 2 to 8 carbon atoms, a trifluoromethyl group, and a substituted or unsubstituted phenyl group, thienyl group, pyridyl group and carbazolyl group) It is represented by Formula (A), The electron transport material of Claim 1 characterized by the above-mentioned.

  An ink composition comprising at least one electron transporting material according to any one of claims 1 to 3 in an organic solvent.   The ink composition according to claim 4, further comprising at least one other kind of carrier transporting material and light emitting material in addition to the material according to any one of claims 1 to 3.   In a light emitting device containing an organic or inorganic light emitting material in at least one layer between opposed electrodes or between an anode and a cathode, at least one layer formed between the opposed electrodes or between the anode and the cathode is claimed. Item 4. A light emitting device comprising the electron transporting material according to any one of Items 1 to 3.   The light-emitting element according to claim 6, wherein the inorganic light-emitting material is a light-emitting element containing an inorganic semiconductor thin film, an inorganic semiconductor fine particle, or a nanorod or nanowire made of an inorganic semiconductor.

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