JP5417702B2 - Organic electroluminescent device, organic electroluminescent layer coating solution, color display device - Google Patents

Description

  The present invention relates to an organic electroluminescent light emitting device and the like, and more particularly to an organic electroluminescent light emitting device having a light emitting layer containing a blue fluorescent compound.

In recent years, organic electroluminescent devices using organic thin films instead of inorganic materials have been developed as thin film type electroluminescent devices. An organic electroluminescent device usually has a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and the like between an anode and a cathode, and materials suitable for these layers have been developed.
Examples of the method for forming each layer include a vacuum deposition method and a wet film forming method. According to the vacuum deposition method, a good quality thin film can be uniformly formed, easy to stack, and has few advantages such as less contamination of impurities.
On the other hand, since the wet film forming method does not require a vacuum process and can easily increase the area, for example, organic electroluminescence has been reported in which an organic thin film layer containing a distyrylarylene derivative is formed by a wet film forming method. (See Patent Document 1).

International Publication No. 03/037836 Pamphlet

By the way, red, green and blue fluorescent compounds are used in the organic electroluminescent device. Among these, the blue fluorescent compound is characterized in that the application is high because the photon of high energy is emitted compared to the red or green fluorescent compound, and the light emitting element in the light emitting state is easily exposed to a high temperature.
Moreover, there exists a problem that the fluorescent compound in a light emitting layer tends to raise | generate a phase change by post process processes, such as a sealing material heat-curing process performed after forming a light emitting layer. For this reason, a fluorescent compound having a high glass transition temperature (Tg) is usually used.
However, a fluorescent compound having a high glass transition temperature (Tg) has a rigid molecular structure and is not affected by a phase change caused by heating and is excellent in extending the life of the device. However, it is soluble in an organic solvent. There is a problem that is low. Therefore, it is difficult to obtain a light emitting layer coating solution used in the wet film forming method.

The present invention has been made to solve the above-described problems.
That is, an object of the present invention is to provide an organic electroluminescent device having a light emitting layer containing a blue fluorescent compound that can be formed by a wet film forming method.
Another object of the present invention is to provide an organic electroluminescent light emitting layer coating solution containing such a blue fluorescent compound.
Another object of the present invention is to provide a color display device having such an organic electroluminescent device.

Thus, according to the present invention, there is provided an organic electroluminescent light emitting device having a light emitting layer containing a light emitting compound between a pair of electrodes, the light emitting compound having a glass transition temperature (Tg) of 80 ° C. or more and An organic electroluminescent light emitting device comprising a blue fluorescent compound having a solubility of 0.2% by weight or more is provided.
Here, in the organic electroluminescent device to which the present invention is applied, the blue fluorescent compound has at least a dinuclear or trinuclear condensed ring (KK1) and a condensed nucleus of 3 to 5 nuclei (KK2). And
The difference between the number of KK2 nuclei and the number of KK1 nuclei is preferably 1 or more and 3 or less.
The blue fluorescent compound preferably has at least an anthracene skeleton, and the anthracene skeleton preferably has a substituent which is unsubstituted at the 2-position and contains at least 5 benzene rings at the 6-position.
Further, the blue fluorescent compound preferably contains at least a luminescent compound having an anthracene skeleton and another luminescent compound having a structure other than the anthracene skeleton.
On the other hand, in the organic electroluminescent device to which the present invention is applied, the light emitting layer is preferably formed by applying a coating solution containing a blue fluorescent compound and a predetermined organic solvent.
The light emitting layer is preferably formed by applying a coating solution containing a blue fluorescent compound and a predetermined organic solvent, and then drying in an environment having an oxygen concentration of 1 ppm or less and a water concentration of 1 ppm or less.
Furthermore, the organic electroluminescent light emitting device to which the present invention is applied has a hole injection layer formed by a wet film forming method between the light emitting layer and the electrode, and the hole injection layer is heated at 200 ° C. or higher. It is preferred that the layer be a layer.

Next, according to the present invention, there is provided an organic electroluminescent light emitting layer coating solution containing a luminescent compound and a predetermined organic solvent, the luminescent compound having a glass transition temperature (Tg) of 80 ° C. or higher and An organic electroluminescent light emitting layer coating solution comprising a blue fluorescent compound having a solubility of 0.2% by weight or more is provided.
Here, the blue fluorescent compound has at least a dinuclear or trinuclear condensed ring (KK1) and a condensed ring of 3 to 5 nuclei (KK2), and the number of KK2 nuclei and the number of KK1 nuclei The difference is preferably 1 or more and 3 or less.
The blue fluorescent compound preferably has at least an anthracene skeleton, and the anthracene skeleton preferably has a substituent which is unsubstituted at the 2-position and contains at least 5 benzene rings at the 6-position.
Further, the blue fluorescent compound preferably contains at least a luminescent compound having an anthracene skeleton and another luminescent compound having a structure other than the anthracene skeleton.

  Furthermore, according to the present invention, a color display device comprising such an organic electroluminescent device is provided.

  In the organic electroluminescent light emitting device of the present invention, the light emitting layer is formed by a wet film forming method.

  The best mode for carrying out the present invention (hereinafter, an embodiment of the present invention) will be described in detail below. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary. The drawings used are for explaining the present embodiment and do not represent the actual size.

(Organic electroluminescent device)
The organic electroluminescent light emitting device to which this embodiment is applied has at least a pair of electrodes (anode, cathode) and a light emitting layer provided between both electrodes on a substrate, and is included in the light emitting layer. The luminescent compound is composed of a blue fluorescent compound having a glass transition temperature (Tg) of 80 ° C. or higher and a solubility in toluene of 0.2% by weight or higher.
Next, each layer of the organic electroluminescence device will be described.

  FIG. 1 is a schematic cross-sectional view showing an example of the structure of an organic electroluminescence device to which the present embodiment is applied. In FIG. 1, 1 is a substrate, 2 is an anode, 3 is a hole injection layer, 4 is a hole transport layer, 5 is a light emitting layer (organic light emitting layer), 6 is a hole blocking layer, 7 is an electron transport layer, 8 Represents an electron injection layer, and 9 represents a cathode.

[1] Substrate The substrate 1 serves as a support for the organic electroluminescent device, and a quartz or glass plate, a metal plate or a metal foil, a plastic film, a sheet, or the like is used. In particular, a glass plate or a transparent synthetic resin plate such as polyester, polymethacrylate, polycarbonate, polysulfone or the like is preferable. When using a synthetic resin substrate, it is necessary to pay attention to gas barrier properties. If the gas barrier property of the substrate is too small, the organic electroluminescent device may be deteriorated by the outside air that has passed through the substrate, which is not preferable. For this reason, a method of providing a gas barrier property by providing a dense silicon oxide film or the like on at least one surface of the synthetic resin substrate is also a preferable method.

[2] Anode An anode 2 is provided on the substrate 1. The anode 2 plays a role of hole injection into a layer on the light emitting layer side (hole injection layer 3 or light emitting layer 5 or the like).
This anode 2 is usually a metal such as aluminum, gold, silver, nickel, palladium, or platinum, a metal oxide such as an oxide of indium and / or tin, a metal halide such as copper iodide, carbon black, or It is composed of a conductive polymer such as poly (3-methylthiophene), polypyrrole, or polyaniline.

In general, the anode 2 is often formed by a sputtering method, a vacuum deposition method, or the like. In addition, when forming an anode using fine metal particles such as silver, fine particles such as copper iodide, carbon black, conductive metal oxide fine particles, and conductive polymer fine powder, an appropriate binder resin solution is used. The anode 2 can also be formed by dispersing and coating the substrate 1. Further, in the case of a conductive polymer, a thin film can be directly formed on the substrate 1 by electrolytic polymerization, or the anode 2 can be formed by applying a conductive polymer on the substrate 1 (Appl. Phys. Lett., 60, 2711, 1992).
The anode 2 usually has a single-layer structure, but it can also have a laminated structure made of a plurality of materials if desired.

  The thickness of the anode 2 varies depending on the required transparency. When transparency is required, the visible light transmittance is usually 60% or more, preferably 80% or more. In this case, the thickness of the anode 2 is usually 5 nm or more, preferably 10 nm or more, and is usually 1000 nm or less, preferably about 500 nm or less. When it may be opaque, the thickness of the anode 2 is arbitrary, and the anode 2 may be the same as the substrate 1. Furthermore, it is also possible to laminate different conductive materials on the anode 2 described above.

  For the purpose of removing impurities adhering to the anode 2 and adjusting the ionization potential to improve the hole injection property, the anode surface is subjected to ultraviolet (UV) / ozone treatment or oxygen plasma or argon plasma treatment. It is preferable.

[3] Hole Injection Layer Since the hole injection layer 3 is a layer that transports holes from the anode 2 to the light emitting layer 5, the hole injection layer 3 preferably contains a hole transporting compound.
The hole injection layer 3 preferably contains a hole transporting compound, and more preferably contains a hole transporting compound and an electron accepting compound. The hole injection layer 3 preferably contains a cation radical compound, and more preferably contains a cation radical compound and a hole transporting compound.
Furthermore, the hole injection layer 3 may contain a binder resin that does not easily trap charges and a coating property improving agent as necessary.

(Hole transporting compound)
As the hole transporting compound, a compound having an ionization potential of 4.5 eV to 6.0 eV is preferable.
Examples of the hole transporting compound include aromatic amine compounds, phthalocyanine derivatives, porphyrin derivatives, oligothiophene derivatives, polythiophene derivatives, and the like. Of these, aromatic amine compounds are preferred from the viewpoints of amorphousness and visible light transmittance.

  An aromatic tertiary amine compound is particularly preferable. Here, the aromatic tertiary amine compound is a compound having an aromatic tertiary amine structure, and includes a compound having a group derived from an aromatic tertiary amine.

The kind of the aromatic tertiary amine compound is not particularly limited, but a polymer compound having a weight average molecular weight of 1,000 or more and 1,000,000 or less (polymerized hydrocarbon compound in which repeating units are linked) is more preferable from the viewpoint of the surface smoothing effect.
Preferable examples of the aromatic tertiary amine polymer compound include a polymer compound having a repeating unit represented by the following general formula (VII).

(In General Formula (VII), Ar ²¹ and Ar ²² each independently represents an aromatic hydrocarbon group which may have a substituent, or an aromatic heterocyclic group which may have a substituent. Ar ^{23 to} Ar ²⁵ each independently represents a divalent aromatic hydrocarbon group which may have a substituent, or a divalent aromatic heterocyclic group which may have a substituent. Y represents a linking group selected from the following group of linking groups, and among Ar ^{21 to} Ar ²⁵ , two groups bonded to the same N atom are bonded to each other to form a ring. May be.)

(In the above formulas, Ar ^{31 to} Ar ⁴¹ are each independently 1 derived from an aromatic hydrocarbon ring which may have a substituent, or an aromatic heterocyclic ring which may have a substituent. And R ⁵¹ and R ⁵² each independently represents a hydrogen atom or an arbitrary substituent.

As Ar ^{21 to} Ar ²⁵ and Ar ^{31 to} Ar ⁴¹ , any monovalent or divalent group derived from any aromatic hydrocarbon ring or aromatic heterocyclic ring is applicable. These may be the same or different from each other. Moreover, you may have arbitrary substituents.

The group derived from the aromatic hydrocarbon ring and / or aromatic heterocycle of Ar ^{21 to} Ar ⁴¹ may further have a substituent. The molecular weight of the substituent is usually 400 or less, preferably about 250 or less.

Ar ²¹ and Ar ²² are preferably monovalent groups derived from a benzene ring, a naphthalene ring, a phenanthrene ring, a thiophene ring, or a pyridine ring from the viewpoint of the solubility, heat resistance, and hole injection / transport properties of the polymer compound. More preferred are a phenyl group and a naphthyl group.

Ar ^{23 to} Ar ²⁵ are preferably divalent groups derived from a benzene ring, a naphthalene ring, an anthracene ring, and a phenanthrene ring from the viewpoint of heat resistance and hole injection / transport properties including redox potential. A group, a biphenylene group, and a naphthylene group are more preferable.

  Specific examples of the aromatic tertiary amine polymer compound having a repeating unit represented by the general formula (VII) include those described in WO2005 / 089024.

The hole transporting compound used as the material for the hole injection layer 3 may contain any one of these compounds alone, or may contain two or more. In the case of containing two or more kinds of hole transporting compounds, the combination is arbitrary, but one or more kinds of aromatic tertiary amine polymer compounds and one or two kinds of other hole transporting compounds. It is preferable to use the above together.
These hole transporting compounds may be appropriately contained in the light emitting layer 5.

(Electron-accepting compound)
The electron-accepting compound is preferably a compound having an oxidizing power and the ability to accept one electron from the above-described hole transporting compound, specifically, a compound having an electron affinity of 4 eV or more is preferable, and 5 eV or more. The compound of is more preferable.

  Examples include onium salts substituted with organic groups such as 4-isopropyl-4′-methyldiphenyliodonium tetrakis (pentafluorophenyl) borate, iron (III) chloride (Japanese Patent Laid-Open No. 11-251067), ammonium peroxodisulfate, etc. High valent inorganic compounds, cyano compounds such as tetracyanoethylene, aromatic boron compounds such as tris (pentafluorophenyl) borane (Japanese Patent Laid-Open No. 2003-31365), fullerene derivatives, iodine and the like.

  Of the above compounds, onium salts substituted with organic groups and high valent inorganic compounds are preferred because of their strong oxidizing power, and organic groups are substituted because they are soluble in various solvents and applicable to wet coating. Preferred are onium salts, cyano compounds, and aromatic boron compounds.

  Specific examples of an onium salt substituted with an organic group, a cyano compound, and an aromatic boron compound suitable as an electron-accepting compound include those described in WO 2005/089024, and suitable examples thereof are also the same. Although the compound (A-2) represented by the following structural formula is mentioned, it is not limited to them at all.

(Cation radical compound)
The cation radical compound is an ionic compound composed of a cation radical which is a chemical species obtained by removing one electron from a hole transporting compound and a counter anion. However, when the cation radical is derived from a hole transporting polymer compound, the cation radical has a structure in which one electron is removed from the repeating unit of the polymer compound.

  The cation radical is preferably a chemical species obtained by removing one electron from the aforementioned compound in the hole transporting compound, and is preferably a chemical species obtained by removing one electron from a compound more preferable as the hole transporting compound. From the viewpoints of visible light transmittance, heat resistance, solubility, and the like.

  The cation radical compound can be generated by mixing the hole transporting compound and the electron accepting compound. That is, by mixing the hole transporting compound and the electron accepting compound, electron transfer occurs from the hole transporting compound to the electron accepting compound, and the cation radical and the counter anion of the hole transporting compound are included. A cation ion compound is formed.

  Cationic radical compounds derived from polymer compounds such as PEDOT / PSS (Adv. Mater., 2000, 12, 481) and emeraldine hydrochloride (J. Phys. Chem., 1990, 94, 7716) It is also produced by oxidative polymerization (dehydrogenation polymerization), that is, by oxidizing the monomer chemically or electrochemically with peroxodisulfate in an acidic solution. In the case of this oxidative polymerization (dehydrogenation polymerization), the monomer is oxidized to be polymerized, and the cation radical is formed by removing one electron from the repeating unit of the polymer with an anion derived from an acidic solution as a counter anion. Produces.

  The hole injection layer 3 is formed on the anode 2 by a wet film forming method or a vacuum deposition method.

  In the case of layer formation by a wet film-forming method, a predetermined amount of one or more of the aforementioned materials (hole transporting compound, electron accepting compound, cation radical compound) is not trapped as necessary. Add binder resin and coatability improver, dissolve in solvent, prepare coating solution, by wet film forming method such as spin coating, spray coating, dip coating, die coating, flexographic printing, screen printing, inkjet method etc. It is applied on the anode 2 and dried to form the hole injection layer 3.

  Here, the drying is preferably performed at 200 ° C. or higher, more preferably 210 ° C. or higher, particularly preferably 230 ° C. or higher, usually 350 ° C. or lower, preferably 280 ° C. or lower. When the drying temperature is excessively low, insolubilization to a solvent tends to be insufficient. When the drying temperature is excessively high, part of the hole injection layer material tends to decompose. The drying time is usually 30 minutes or longer, preferably 1 hour or longer, preferably 3 hours or shorter, more preferably 1 hour or shorter. When the drying time is excessively short, insolubilization to the solvent tends to be insufficient.

  As the solvent used for the layer formation by the wet film forming method, any solvent can be used as long as it can dissolve the above-mentioned materials (hole transporting compound, electron accepting compound, cation radical compound). Is not particularly limited, but generates a deactivated substance or deactivated substance that may deactivate each material (hole transporting compound, electron accepting compound, cation radical compound) used for the hole injection layer 3 What does not contain a thing is preferable. An ether solvent or an ester solvent is preferable.

In the case of forming a layer by vacuum deposition, one or more of the aforementioned materials (hole transporting compound, electron accepting compound, cation radical compound) are put in a crucible installed in a vacuum vessel ( When two or more materials are used, put them in each crucible), and after evacuating the inside of the vacuum vessel to about 10 ⁻⁴ Pa with an appropriate vacuum pump, heat the crucible (if using two or more materials, each The crucible is heated), the amount of evaporation is controlled and evaporated (when two or more materials are used, the amount of evaporation is controlled independently), and the substrate is placed on the anode 2 facing the crucible. A hole injection layer 3 is formed. When two or more kinds of materials are used, a mixture of them can be put in a crucible, heated and evaporated to be used for forming the hole injection layer 3.

  The film thickness of the hole injection layer 3 thus formed is usually in the range of 5 nm or more, preferably 10 nm or more, and usually 1000 nm or less, preferably 500 nm or less. The hole injection layer 3 may be omitted.

[4] Hole Transport Layer The hole transport layer 4 is provided on the hole injection layer 3. The material of the hole transport layer 4 needs to be a material that has a high hole injection efficiency from the anode 2 and can efficiently transport the injected holes. For this purpose, the ionization potential is low, the transparency to visible light is high, the hole mobility is high, the stability is high, and impurities that become traps are unlikely to be generated during manufacturing or use. Required. Further, in order to contact the light emitting layer 5, it is required not to quench the light emitted from the light emitting layer 5 or to form an exciplex with the light emitting layer 5 to reduce the efficiency. In addition to the above general requirements, when the application for in-vehicle display is considered, the element is further required to have heat resistance. Accordingly, a material having a glass transition temperature (Tg) of 85 ° C. or higher is desirable.

  Examples of such a hole transporting material include two or more condensed fragrances including two or more tertiary amines represented by 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl. Aromatics having a starburst structure such as aromatic diamines substituted with nitrogen atoms in the aromatic ring (Japanese Patent Laid-Open No. 5-234681), 4,4 ′, 4 ″ -tris (1-naphthylphenylamino) triphenylamine, etc. Amine compounds (J. Lumin., 72-74, 985, 1997), aromatic amine compounds consisting of tetramers of triphenylamine (Chem. Commun., 2175, 1996), 2, 2 ′ , 7,7'-Tetrakis- (diphenylamino) -9,9'-spirobifluorene, etc. (Synth. Metals, 91, 209, 1997) , 4,4'-N, such as a carbazole derivative such as N'- dicarbazole biphenyl. These compounds may be used individually by 1 type, and may be used in mixture of multiple types as needed.

  In addition to the above compounds, polyarylene ether sulfone (Polym. Adv. Tech.) Containing polyvinyl carbazole, polyvinyl triphenylamine (Japanese Patent Laid-Open No. 7-53953), and tetraphenylbenzidine as a material for the hole transport layer 4. 7, Vol. 33, 1996).

The hole transport layer 4 is obtained by polymerizing a compound having a polymerizable group (polymerizable compound) by irradiation with heat and / or active energy rays (ultraviolet rays, electron beams, infrared rays, microwaves, etc.). A layer is preferred.
Here, the “polymerizable group” refers to a group that reacts with the same or different groups of other molecules located in the vicinity by irradiation with heat and / or active energy rays to form a new chemical bond. Although it does not specifically limit as a polymeric group, For example, group containing an unsaturated double bond, cyclic ether, benzocyclobutane etc. is preferable.
Examples of the polymerizable compound include monomers, oligomers, and polymers having the above-described polymerizable group. Among them, monomers are preferable.

Specific examples of the polymerizable compound, for example, triarylamine derivatives, carbazole derivatives, fluorene derivatives, 2,4,6-triphenyl pyridine derivatives, C ₆₀ derivatives, oligothiophene derivatives, phthalocyanine derivatives, porphyrin derivatives, condensed polycyclic An aromatic derivative, a metal complex derivative, etc. are mentioned. Among these, a compound having a partial structure of triphenylamine and a polymerizable group is particularly preferable because of high electrochemical stability and charge transportability.

  The hole transport layer 4 may be formed by a normal coating method such as a spray method, a printing method, a spin coating method, a dip coating method, or a die coating method, a wet film forming method such as an ink jet method or a screen printing method, or a vacuum coating method. It can be formed by a dry film forming method such as a vapor deposition method.

  In the case of a wet film-forming method, an additive such as a binder resin or a coating property improving agent that does not trap holes is added to one or more hole transport materials as necessary, and dissolved in a suitable solvent. Then, a coating solution is prepared, applied onto the anode 2 by a method such as spin coating, and dried to form the hole transport layer 4. Examples of the binder resin include polycarbonate, polyarylate, and polyester. When the amount of the binder resin added is large, the hole mobility is lowered. Therefore, the smaller amount is desirable, and the content in the hole transport layer is usually preferably 50% by weight or less.

In the case of the vacuum deposition method, the hole transport material is put in a crucible installed in a vacuum vessel, the inside of the vacuum vessel is evacuated to about 10 ⁻⁴ Pa with a suitable vacuum pump, and then the crucible is heated, The hole transport material is evaporated and the hole transport layer 4 is formed on the substrate 1 on which the anode 2 or the hole injection layer 3 is formed, which is placed facing the crucible.

The thickness of the hole transport layer 4 is usually 5 nm or more, preferably 10 nm or more, and is usually 300 nm or less, preferably 100 nm or less. In order to uniformly form such a thin film, a vacuum deposition method is generally used.
The hole transport layer 4 is not necessarily provided, and a light emitting layer 5 described later may be directly formed on the hole injection layer 3.

[5] Light emitting layer (organic light emitting layer)
A light emitting layer 5 (organic light emitting layer) is provided on the hole transport layer 4. The light-emitting layer 5 contains a light-emitting compound, and includes holes injected from the anode 2 through the hole injection layer 3 and electrons injected from the cathode 9 through the electron injection layer 8 between the electrodes to which an electric field is applied. Excited by recombination and becomes the main light source. The light emitting layer 5 preferably contains a light emitting compound (dopant) and one or more host materials.

In the present embodiment, the light-emitting compound contained in the light-emitting layer 5 has a glass transition temperature (Tg) of 80 ° C. or higher, preferably 100 ° C. or higher, more preferably 115 ° C. or higher, and particularly preferably 130 ° C. The blue fluorescent compound has a solubility in toluene of 0.2% by weight or more, preferably 0.6% by weight or more, and more preferably 1.5% by weight or more.
Here, the blue fluorescent compound emits blue light in an electric field in the light emitting layer 5, and is used alone or in combination as a dopant or a host. The glass transition temperature (Tg) of the blue fluorescent compound is measured by a differential scanning calorimeter. The solubility in toluene is at 25 ° C.
Such a blue fluorescent compound is a compound having 2 to 15 condensed or non-condensed benzene rings which may have a substituent, and has a molecular weight of preferably 400 to 1,000, more preferably Includes 400 to 800 compounds.

In the present embodiment, the blue fluorescent compound has at least a dinuclear or trinuclear condensed ring (KK1) and a condensed nucleus of 3 to 5 nuclei (KK2). The number of KK2 nuclei and KK1 A compound having a difference from 1 to 3 is preferable. By satisfying this range, the solubility in an organic solvent is improved while maintaining a high glass transition temperature, and the luminous efficiency is further improved. The molecular structure of the blue fluorescent compound preferably has an asymmetric skeleton.
More specifically, an aminostilbene compound, a fluorene compound, an anthracene compound, a naphthalene compound, a pyrene compound, a perylene compound, a chrysene compound which may have a substituent may be mentioned.
Hereinafter, specific compounds will be described.

(1) Aminostilbene compound (1-1) Diaminostilbene compound Examples of the diaminostilbene compound which may have a substituent include compounds represented by the following formula (1).

In formula (1), R _{1 to} R ₄ each independently represents an aromatic condensed ring group. The aromatic condensed ring group is preferably a group derived from a condensed ring having 2 to 5 nuclei. Specific examples include a naphthalene ring, anthracene ring, phenanthrene ring, fluorene ring, fluoranthene ring, tetracene ring, pyrene ring, benzpyrene ring, chrysene ring, triphenylene ring, and perylene ring. Among these, a naphthalene ring and a phenanthrene ring are preferable.

R _{1 to} R ₄ may be bonded to an adjacent group or a mother skeleton part directly or via a nitrogen atom to form a ring.
Moreover, in Formula (1), it is preferable that a molecule | numerator does not have a symmetry. It is particularly preferable that (i) R ₁ = R ₂ , R ₃ = R ₄ , R ₁ ≠ R ₄ , (ii) R ₁ ≠ R ₂ , R ₃ ≠ R ₄ .
Furthermore, in R _{1 to} R ₄ , when at least one is a condensed ring (KK1) having 2 to 3 nuclei and at least one is a condensed ring (KK2) having 3 to 5 nuclei, 1 ≦ [[(KK2 ))-[(Number of nuclei of (KK1)]] ≦ 3. By satisfying this range, the solubility in an organic solvent is improved while maintaining a high glass transition temperature, and the luminous efficiency is further improved.

Here, R _{1 to} R ₄ may further have a substituent. Examples of the substituent that R _{1 to} R ₄ may have include the following (hereinafter, may be referred to as “substituent group A”).
For example, an alkyl group which may have a substituent (preferably a linear or branched alkyl group having 1 to 8 carbon atoms, such as methyl, ethyl, n-propyl, 2-propyl, n- Butyl, isobutyl, tert-butyl group, etc.); an alkenyl group which may have a substituent (preferably an alkenyl group having 2 to 9 carbon atoms, such as vinyl, allyl, 1- An alkynyl group which may have a substituent (preferably an alkynyl group having 2 to 9 carbon atoms, such as an ethynyl group or a propargyl group);

An aralkyl group which may have a substituent (preferably an aralkyl group having 7 to 15 carbon atoms, such as a benzyl group); an acyl group which may have a substituent ( Preferably, it is an acyl group having 2 to 10 carbon atoms which may have a substituent, and examples thereof include formyl, acetyl and benzoyl groups); alkoxycarbonyl which may have a substituent A group (preferably an alkoxycarbonyl group having 2 to 10 carbon atoms which may have a substituent, such as methoxycarbonyl, ethoxycarbonyl group, etc.); A good aryloxycarbonyl group (preferably an aryloxycarbonyl group having 6 to 15 carbon atoms which may have a substituent, for example, phenoxycarbonyl Group and the like);

Halogen atom (especially fluorine atom or chlorine atom); carboxy group; optionally substituted aromatic hydrocarbon group (for example, benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, perylene ring, tetracene ring, And monovalent groups derived from a 5-membered or 6-membered monocyclic ring or a 2 condensed ring to a 5 condensed ring, such as a pyrene ring, a benzpyrene ring, a chrysene ring, a triphenylene ring, and a fluoranthene ring).

An aromatic heterocyclic group which may have a substituent (for example, furan ring, benzofuran ring, thiophene ring, benzothiophene ring, pyrrole ring, pyrazole ring, imidazole ring, oxadiazole ring, indole ring, carbazole ring, Pyrroloimidazole ring, pyrrolopyrazole ring, pyrrolopyrrole ring, thienopyrrole ring, thienothiophene ring, furopyrrole ring, furofuran ring, thienofuran ring, benzoisoxazole ring, benzoisothiazole ring, benzimidazole ring, pyridine ring, pyrazine ring, pyridazine ring , Pyrimidine ring, triazine ring, quinoline ring, isoquinoline ring, sinoline ring, quinoxaline ring, benzimidazole ring, perimidine ring, quinazoline ring, etc. A monovalent group). It is below.

  Examples of the substituent that each group of the substituent group A described above may have include, for example, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, and 6 to 10 carbon atoms. An aryloxy group containing an aromatic hydrocarbon group, an alkylamino group having at least one alkyl group having 1 to 6 carbon atoms, an aromatic hydrocarbon group having 6 to 20 carbon atoms, and 1 to carbon atoms 6 alkylthio groups, arylthio groups having 6 to 10 carbon atoms aromatic hydrocarbon groups, acyl groups having 2 to 20 carbon atoms, and the like.

  Specific examples of the diaminostilbene compound which may have a substituent include the following compounds.

(1-2) Monoaminostilbene Examples of the monoaminostilbene compound which may have a substituent include compounds represented by the following formula (1-2).

In formula (1-2), R ₂₁ and R ₂₂ each independently represents an aromatic hydrocarbon group which may have a substituent. R ₂₃ represents an aromatic hydrocarbon group which may have a substituent. m represents an integer of 0 to 3. When m is 2 or 3, the plurality of R ₂₃ may be the same or different.
Examples of the aromatic hydrocarbon group optionally having a substituent of R _{21 to} R ₂₃ include a benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, perylene ring, tetracene ring, pyrene ring, benzpyrene ring, chrysene And monovalent groups derived from 5-membered or 6-membered monocycles such as a ring, a triphenylene ring, and a fluoranthene ring, or from 2 condensed rings to 5 condensed rings.
In addition, examples of the substituent that the aromatic hydrocarbon group may have include the groups described in the above substituent group A. Specific examples are given below.

(2) Fluorene compound As a fluorene compound which may have a substituent, the compound represented by following formula (2) is mentioned.

In formula (2), R ₅ and R ₆ are each independently selected from a diarylamino group or a substituent described as the substituent group A described above. Among these, a diarylamino group is particularly preferable.
The aryl group bonded to the amino group includes a benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, fluorene ring, fluoranthene ring, tetracene ring, pyrene ring, benzpyrene ring, chrysene ring, triphenylene ring, perylene ring, etc. Examples include a ring or a group derived from a 6-membered monocyclic ring or a 2 to 5 condensed ring. Particularly preferred are a benzene ring, naphthalene ring and phenanthrene ring. The two aryl groups of the diarylamino group may be the same or different, but are preferably different. R ₅ and R ₆ are preferably the same.

R ₇ and R ₈ are each independently an alkyl group that may have a substituent, an aromatic hydrocarbon group that may have a substituent, or an aromatic complex that may have a substituent. Represents a cyclic group. R ₇ and R ₈ may be bonded to each other directly or through a substituent bonded thereto to form a ring.
Here, the alkyl group which may have a substituent is usually a linear or branched alkyl group having 1 to 8 carbon atoms, such as methyl, ethyl, n-propyl, 2-propyl. , N-butyl, isobutyl, tert-butyl group and the like. A methyl group is preferred.

Examples of the aromatic hydrocarbon group which may have a substituent include benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, perylene ring, tetracene ring, pyrene ring, benzpyrene ring, chrysene ring, triphenylene ring, fluoranthene. Examples thereof include a monovalent group derived from a 5-membered ring such as a ring or a 6-membered monocyclic ring or a 2 condensed ring to a 5 condensed ring.
Examples of the aromatic heterocyclic group which may have a substituent include a furan ring, a benzofuran ring, a thiophene ring, a benzothiophene ring, a pyrrole ring, a pyrazole ring, an imidazole ring, an oxadiazole ring, an indole ring, and a carbazole. Ring, pyrroloimidazole ring, pyrrolopyrazole ring, pyrrolopyrrole ring, thienopyrrole ring, thienothiophene ring, furopyrrole ring, furofuran ring, thienofuran ring, benzoisoxazole ring, benzoisothiazole ring, benzimidazole ring, pyridine ring, pyrazine ring, Pyridazine ring, pyrimidine ring, triazine ring, quinoline ring, isoquinoline ring, sinoline ring, quinoxaline ring, benzimidazole ring, perimidine ring, quinazoline ring, etc. Monovalent group derived from .

Examples of these substituents include the substituents described in the substituent group A described above.
N represents an integer of 1 to 5, and is preferably 3. The n fluorene rings may have a substituent. The n fluorene rings may be the same or different.

  Furthermore, examples of the fluorene compound which may have a substituent include compounds having the following skeleton.

  Specific examples of the fluorene compound which may have a substituent include the following compounds.

(2-1) Bisfluorene compound In this Embodiment, the bisfluorene compound represented by following formula (2-1) is preferable among the fluorene compounds which may have a substituent.

  Specific examples of the bisfluorene compound represented by the formula (2-1) include the following compounds. Hereinafter, Np represents a naphthalene ring and Phen represents a phenanthrene ring.

(3) Anthracene compound As an anthracene compound which may have a substituent, a 9,10 substituent anthracene compound represented by the following formula (3) may be mentioned.

In formula (3), R ₉ and R ₁₀ each independently represents an aromatic hydrocarbon group which may have a substituent.
Examples of the aromatic hydrocarbon group which may have a substituent include a benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, perylene ring, tetracene ring, pyrene ring, benzpyrene ring, chrysene ring, triphenylene ring, and fluoranthene ring. And monovalent groups derived from a 5-membered ring or a 6-membered monocyclic ring or a 2 condensed ring to a 5 condensed ring.
Substituents R ₉ and _{R 10} each may have a _{R 9} and _{R 10} and / or bonded to the anthracene ring to form a ring.
In addition, the anthracene ring may have a substituent, and examples of such a substituent include those described in the substituent group A described above.
Specific examples of the 9,10-substituted anthracene compound represented by the formula (3) include the following compounds.

(3-1, 3-2)
In this embodiment, among the anthracene compounds which may have a substituent, a 6,9,10-substituted anthracene compound represented by the following formula (3-1) or a formula (3-2) 2,6,9,10 substituted anthracene compounds are preferred.
In particular, the anthracene skeleton is preferably an anthracene compound having a substituent which is unsubstituted at the 2-position and contains at least 5 benzene rings at the 6-position.

In Formula (3-1) and Formula (3-2), examples of R ₁₁ , R _11a, and R ₁₂ include the substituents described in Substituent Group A described above. In Formula (3-1) or Formula (3-2), R ₉ and R ₁₀ are preferably phenyl groups. R ₁₁ , R _11a and R ₁₂ are each preferably an aromatic hydrocarbon group which may have a substituent, preferably a dinuclear to tetranuclear condensed ring or / and 5 or more benzene rings. It is preferable to have it. In particular, R _11a preferably has 5 or more benzene rings.

  Here, what has 5 or more benzene rings may be a structure in which a plurality of benzene rings are connected (for example, biphenyl group, terphenyl group, etc.), or condensed by condensation of benzene rings. A ring formed (for example, naphthalene ring, anthracene ring, etc.) may be used, or a combination thereof may be used.

  Specific examples of the 2,6,9,10-substituted anthracene compound represented by the formula (3-2) include the following compounds. Np represents a naphthalene ring. In addition to these, those exemplified as specific examples of the formula (3) can be given.

(3-3) Bianthracene Compound In the present embodiment, among the anthracene compounds that may have a substituent, a bianthracene compound represented by the following formula (3-3) is preferable.

In formula (3-3), R ₁₃ and R ₁₄ each independently represents an aromatic hydrocarbon group which may have a substituent.
Examples of the aromatic hydrocarbon group which may have a substituent include a benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, perylene ring, tetracene ring, pyrene ring, benzpyrene ring, chrysene ring, triphenylene ring, and fluoranthene ring. And monovalent groups derived from a 5-membered ring or a 6-membered monocyclic ring or a 2 condensed ring to a 5 condensed ring. Among these, a benzene ring is preferable.

Substituents R ₁₃ and _{R 14} each _may have a _{R 13} and _{R 14} and / or bonded to the anthracene ring to form a ring.
In addition, the anthracene ring may have a substituent, and examples of such a substituent include those described in the substituent group A described above. Furthermore, the anthracene ring substituents may be bonded to each other to form a ring.

  Specific examples of the bianthracene compound represented by the formula (3-3) include the following compounds.

(3-4) Other Anthracene Compounds In the present embodiment, among the anthracene compounds that may have a substituent, an anthracene compound represented by the following formula (3-4) is preferable.

In the formula (3-4), R ₁₅ and R ₁₆ are each independently selected from a hydrogen atom or a substituent described in the substituent group A described above. R ₁₅ and / or R ₁₆ is preferably a substituent.
In addition to R ₁₅ and R ₁₆ , the anthracene ring or benzene ring may have a substituent. Examples of such a substituent include those described in the substituent group A described above.
Specific examples of the anthracene compound represented by the formula (3-4) include the following compounds.

  In the present embodiment, examples of the anthracene compound which may have a substituent further include the following anthracene compounds.

(4) Naphthalene compound As a naphthalene compound which may have a substituent, a naphthalene compound having a diarylamino group represented by the following formula (4) may be mentioned.

In formula (4), R < ₁₇ > -R < ₂₀ > represents the aromatic hydrocarbon group which may have a substituent each independently.
Examples of the aromatic hydrocarbon group which may have a substituent include a benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, perylene ring, tetracene ring, pyrene ring, benzpyrene ring, chrysene ring, triphenylene ring, and fluoranthene ring. And monovalent groups derived from a 5-membered ring or a 6-membered monocyclic ring or a 2 condensed ring to a 5 condensed ring.
Examples of the substituent of R _{17 to} R ₂₀ include the substituents described in the substituent group A and the diarylamino group.
The —NR ₁₇ R ₁₈ group and the —NR ₁₉ R ₂₀ group are preferably bonded to the 2nd and 6th positions of the naphthalene ring, respectively.
Specific examples of the naphthalene compound having a diarylamino group represented by the formula (4) include the following compounds.

(5) Other compounds Further, in the present embodiment, the compound has at least a dinuclear or trinuclear condensed ring (KK1) and a condensed nucleus of 3 to 5 nuclei (KK2), and the number of KK2 nuclei Examples of blue fluorescent compounds having a difference from the number of KK1 nuclei of 1 to 3 include the following compounds.

(6) Pyrene compound Examples of the pyrene compound which may have a substituent include the compounds exemplified below.

In the above formula, R _{84 to} R ₈₇ are selected from a hydrogen atom or a group described in the substituent group A. R _{84 to} R ₈₇ may be the same or different from each other. R _{84 to} R ₈₇ are particularly preferably aromatic hydrocarbon groups which may have a substituent. _Also, as in such _{R 84} ≠ _{R 85} or _{R 84} ≠ _{R 87,} it is preferably asymmetric structure.

(7) Examples of the perylene compound which may have a substituent include compounds exemplified below.

In the formula, R _{25 to} R ₃₂ are selected from a hydrogen atom or an alicyclic hydrocarbon group and a group described in the substituent group A. R _{25 to} R ₃₂ may be the same or different from each other.
The alicyclic hydrocarbon group is preferably an alicyclic hydrocarbon group having 5 to 8 carbon atoms, and specific examples include a cyclohexyl group and a cyclopentyl group.
Moreover, among the said substituent group A, an alkyl group is preferable, Especially the alkyl group which has a tertiary carbon atom or a quaternary carbon atom in a group is preferable, and a C4-C15 alkyl group is especially preferable. In the following specific examples, Me represents a methyl group.

(8) Chrysene compound Furthermore, the chrysene compound illustrated below.

(In the above formula, R _{33 to} R ₄₀ , R _{43 to} R ₄₆ , and R _{49 to} R ₅₂ each independently represents an aromatic hydrocarbon group which may have a substituent. R ₄₁ and R _42. , R ₄₇ and R ₄₈ each independently represents an aromatic hydrocarbon group which may have a substituent or an alkyl group which may have a substituent.

Specific examples of the aromatic hydrocarbon group which may have a substituent of R _{33 to} R ₅₂ include those exemplified as the aromatic hydrocarbon group for R _{17 to} R ₂₀ . Moreover, as a substituent, the substituent described in the substituent group A mentioned above is mentioned.
Specific examples of the alkyl group which may have a substituent of R ₄₁ , R ₄₂ , R ₄₇ , and R ₄₈ are preferably a linear or branched alkyl group having 1 to 8 carbon atoms, For example, methyl group, ethyl group, n-propyl group, n-butyl group, isobutyl group, tert-butyl group and the like can be mentioned.

  Specifically, the following compounds are mentioned.

  Further, in the structure of the specific example of the chrysene compound, instead of the following group bonded to the amino group,

It may have a group described in the following substituent group a.

(9) Compound having an aliphatic ring Examples of the compound having an aliphatic ring include compounds represented by the following formulae.

(In the formula, Ar ¹ represents an aromatic condensed ring group selected from the group consisting of naphthalene, phenanthrene, chrysene, and pyrene. Y ¹ represents a hydrogen atom or an aromatic hydrocarbon group. Ring X ¹ represents an aliphatic group. Represents an aromatic ring, and n represents an integer of 1 or more.)

Ar ¹ may have a substituent, and examples of the substituent include the groups described in the substituent group A described above.
Examples of the aromatic hydrocarbon group for Y ¹ include groups derived from a benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, perylene ring, tetracene ring, pyrene ring, benzpyrene ring, chrysene ring, triphenylene ring, fluoranthene ring, and the like. Can be mentioned. These aromatic hydrocarbon groups may have a substituent, and examples of the substituent include the groups described in the substituent group A described above.
The ring X ¹ aliphatic ring, for example, cyclobutane, cyclopentane, cyclohexane.
n represents an integer of 1 or more, preferably 4 or less, more preferably 2 or less, and particularly preferably 2.

Next, a specific example is shown.
Table 1 shows compounds 1 to 6 having an arylamino group, a hydrogen atom, and an ethyl group as substituents R ₆₁ to R ₇₀ in the compounds having an aliphatic ring represented by the following chemical formula (EqI).

  Here, in Table 1, -H represents a hydrogen atom. The arylamino groups CM1 to CM6 are as follows.

Table 2 shows compounds 7 to 14 having an arylamino group, a hydrogen atom, and an ethyl group as substituents R ₇₁ to R ₈₂ in the compounds having an aliphatic ring represented by the following chemical formula (EqII).

  Here, in Table 2, -H represents a hydrogen atom, and ET represents an ethyl group. The arylamino groups CM1 to CM6 are as described above.

Table 3 shows compounds 15 to 26 having an arylamino group and a hydrogen atom as substituents R ₉₁ to R ₁₀₀ in the compounds having an aliphatic ring represented by the following chemical formula (EqIV).

  Here, in Table 3, -H represents a hydrogen atom. The arylamino groups CM1 to CM6 are as described above.

Table 4 shows compounds 27 to 44 each having an arylamino group and a hydrogen atom as substituents R ₁₀₁ to R ₁₀₈ in the compounds having an aliphatic ring represented by the following chemical formula (EqVII).

  Here, in Table 4, -H represents a hydrogen atom. The arylamino groups CM1 to CM6 are as described above.

  In the present embodiment, the compounds of (1) to (9) mentioned as blue fluorescent compounds may be further appropriately selected from substituent group A described above, if necessary. Good.

In the present embodiment, the blue fluorescent compounds described above may be used alone, or two or more blue fluorescent compounds may be used in combination.
In particular, in the present embodiment, as the blue fluorescent compound contained in the light emitting layer 5, it is preferable to use a combination of at least a blue fluorescent compound having an anthracene skeleton and another blue fluorescent compound having a structure other than the anthracene skeleton. .

In this case, the mixing ratio (A / B) of the blue fluorescent compound (A) having at least an anthracene skeleton and the other blue fluorescent compound (B) having a structure other than the anthracene skeleton is not particularly limited.
For example, when the ratio of the blue fluorescent compound (A) component having an anthracene skeleton is large and the mixing ratio (A / B) is (90/10) <(A / B) <100, the organic electroluminescent device is long. There is a tendency to have a long life. Further, when the ratio of the other blue fluorescent compound (B) component having a structure other than the anthracene skeleton is increased and the mixing ratio (A / B) is smaller than (90/10) ((A / B) <(90 / 10)), the luminous efficiency of the light emitting layer 5 tends to increase.

In the present embodiment, the light emitting layer 5 of the organic electroluminescent element is prepared by applying a coating solution (organic electroluminescent light emitting layer coating solution) containing the above-described blue fluorescent compound and a predetermined organic solvent by a wet film forming method. It is formed by coating on the hole injection layer 3 or the hole transport layer 4 formed on or on the anode 2. If the hole transport layer 4 is not provided, it is formed by coating on the hole injection layer 3.
When the light-emitting layer 5 is formed by a wet film-forming method, a predetermined amount of one or two or more blue fluorescent compounds is dissolved in a solvent, if necessary, a binder resin that does not trap charges or a coating property improver. An organic electroluminescent light emitting layer coating solution is prepared, and this is applied onto the anode 2 by a wet film forming method such as spin coating, spray coating, dip coating, die coating, flexographic printing, screen printing, and inkjet method, and dried. The light emitting layer 5 is formed.

The organic electroluminescent layer coating solution may further contain a hole transport material. Examples of the hole transport material include those exemplified as the hole transport material used for the hole transport layer 4. Of these, aromatic amine compounds are preferable, and triarylamine compounds are particularly preferable.
The content of the hole transport material in the organic electroluminescent layer coating solution is preferably 0.1% by weight to 20% by weight, and more preferably 0.5% by weight to 10% by weight.
When the light emitting layer 5 is formed by a wet film forming method, the film formation is usually 10 ° C. or higher, preferably 13 ° C. or higher, more preferably 16 ° C. or higher, usually 50 ° C. or lower, preferably 40 ° C. or lower, more preferably 30 ° C. It is done in the following. The relative humidity is usually 0.01% or more, preferably 0.05% or more, preferably 80% or less, more preferably 60% or less. Moreover, oxygen concentration is 0.01 ppm or more normally, More preferably, it is 0.05 ppm or more, Preferably it is 50% or less, More preferably, it is 25% or less.

  In the present embodiment, various solvents can be used as the solvent contained in the organic electroluminescent light emitting layer coating solution described above, and are not particularly limited.

  For example, aromatic hydrocarbons such as toluene, xylene, methicylene, cyclohexylbenzene and tetralin; halogenated aromatic hydrocarbons such as chlorobenzene, dichlorobenzene and trichlorobenzene; 1,2-dimethoxybenzene, 1,3-dimethoxybenzene and anisole , Phenetole, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2,3-dimethylanisole, 2,4-dimethylanisole and other aromatic ethers; phenyl acetate, phenyl propionate, methyl benzoate, benzoic acid Aromatic esters such as ethyl, propyl benzoate and n-butyl benzoate; ketones having an alicyclic ring such as cyclohexanone and cyclooctanone; aliphatic ketones such as methyl ethyl ketone and dibutyl ketone; methyl ethyl ketone and cyclohexano Alcohol having an alicyclic ring such as ruthenium or cyclooctanol; Aliphatic alcohol such as butanol or hexanol; Aliphatic ether such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether or propylene glycol-1-monomethyl ether acetate (PGMEA); Ethyl acetate And aliphatic esters such as n-butyl acetate, ethyl lactate and n-butyl lactate.

  Of these, aromatic hydrocarbons such as toluene, xylene, methicylene, cyclohexylbenzene, and tetralin are preferred because they have low water solubility and do not easily change quality. This is preferable because it is easy to form a light emitting layer of an organic electroluminescent device having excellent film thickness uniformity.

Since organic electroluminescent light emitting elements use many materials such as cathodes that deteriorate significantly due to moisture, the presence of moisture in the organic electroluminescent light emitting layer coating solution leaves moisture in the dried film, There is a possibility of deteriorating the characteristics of the element, which is not preferable.
Examples of a method for reducing the amount of water in the organic electroluminescent layer coating solution include nitrogen gas sealing, use of a desiccant, dehydration of the solvent in advance, use of a solvent with low water solubility, and the like. In particular, it is preferable to use a solvent having low water solubility because the solution film can prevent whitening by absorbing moisture in the atmosphere during the wet film-forming process. From such a viewpoint, for example, it is preferable to contain 10% by weight or more of a solvent having a water solubility at 25 ° C. of 1% by weight or less, preferably 0.1% by weight or less.

Further, in order to prevent the film formation stability from being reduced by evaporation of the solvent during wet film formation, the boiling point is 100 ° C. or higher, preferably the boiling point is 150 ° C. or higher, more preferably the boiling point is 200 ° C. or higher. It is effective to use a solvent.
In order to obtain a more uniform film, it is necessary for the solvent to evaporate from the liquid film immediately after film formation at an appropriate rate. For this purpose, the boiling point is usually 80 ° C. or higher, preferably 100 ° C. or higher. It is effective to use a solvent having a boiling point of 120 ° C. or more, usually less than 270 ° C., preferably less than 250 ° C., more preferably less than 230 ° C. A solvent can also be used individually or in mixture of 2 or more types of solvents.
In order to obtain a more uniform film, vacuum drying, heat drying, optimization of time from film formation to drying treatment, and the like can be performed as necessary. Drying is preferably performed in an environment having an oxygen concentration of 1 ppm or less and a water concentration of 1 ppm or less.

  In the present embodiment, in addition to the light emitting layer 5, when an organic layer such as the hole injection layer 3 and the electron injection layer 8 described later is provided, the light emitting layer 5, the hole injection layer 3, and the electron injection layer 8 other than The total film thickness combined with the organic layer is usually 30 nm or more, preferably 50 nm or more, more preferably 100 nm or more, usually 1000 nm or less, preferably 500 nm or less, and more preferably 300 nm or less. In addition, when the conductivity of the hole injection layer 3 other than the light emitting layer 5 and the electron injection layer 8 described later is high, the amount of charge injected into the light emitting layer 5 increases. It is also possible to reduce the drive voltage while increasing the thickness to reduce the thickness of the light emitting layer 5 while maintaining the total thickness to some extent.

  Therefore, the film thickness of the light emitting layer 5 is usually 10 nm or more, preferably 20 nm or more, and usually 300 nm or less, preferably 200 nm or less. When the element of the present invention has only the light emitting layer 5 between the anode 2 and the cathode 9, the thickness of the light emitting layer 5 is usually 30 nm or more, preferably 50 nm or more, usually 500 nm or less, preferably 300 nm. It is as follows.

[6] Hole blocking layer The hole blocking layer 6 has a function of confining holes and electrons in the light emitting layer 5 and improving luminous efficiency. That is, the hole blocking layer 6 is generated by increasing the recombination probability with electrons in the light emitting layer 5 by blocking the holes moving from the light emitting layer 5 from reaching the electron transport layer 7. There is a role of confining excitons in the light emitting layer 5 and a role of efficiently transporting electrons injected from the electron transport layer 7 in the direction of the light emitting layer 5.

  The hole blocking layer 6 can prevent holes moving from the anode 2 from reaching the cathode 9 and can efficiently transport electrons injected from the cathode 9 toward the light emitting layer 5. The compound is laminated on the light emitting layer 5 so as to be in contact with the interface of the light emitting layer 5 on the cathode 9 side.

  The physical properties required for the material constituting the hole blocking layer 6 include high electron mobility, low hole mobility, a large energy gap (difference between HOMO and LUMO), and excited triplet level (T1). Is high.

  Examples of the material of the hole blocking layer 6 that satisfies such conditions include bis (2-methyl-8-quinolinolato) (phenolato) aluminum, bis (2-methyl-8-quinolinolato) (triphenylsilanolato) aluminum, and the like. Mixed ligand complexes, metal complexes such as bis (2-methyl-8-quinolato) aluminum-μ-oxo-bis- (2-methyl-8-quinolinato) aluminum binuclear metal complexes, styryls such as distyrylbiphenyl derivatives Compounds (JP-A-11-242996), triazole derivatives such as 3- (4-biphenylyl) -4-phenyl-5 (4-tert-butylphenyl) -1,2,4-triazole (JP-A-7- 41759) and phenanthroline derivatives such as bathocuproine (Japanese Patent Laid-Open No. 10-79297).

  Furthermore, a compound having at least one pyridine ring substituted at the 2,4,6-positions described in WO05 / 022962 is also preferable as the hole blocking material.

  The film thickness of the hole blocking layer 6 is usually 0.3 nm or more, preferably 0.5 nm or more, and usually 100 nm or less, preferably 50 nm or less. The hole blocking layer 6 can be formed by the same method as the hole injection layer 3, but usually a vacuum deposition method is used.

[7] Electron Transport Layer The electron transport layer 7 is provided between the light emitting layer 5 and the electron injection layer 8 for the purpose of further improving the light emission efficiency of the device.
The electron transport layer 7 is formed of a compound that can efficiently transport electrons injected from the cathode 9 between electrodes to which an electric field is applied in the direction of the light emitting layer 5. As the electron transporting compound used for the electron transport layer 7, the electron injection efficiency from the cathode 9 or the electron injection layer 8 is high, and the injected electrons can be efficiently transported with high electron mobility. It must be a compound.

  Materials satisfying such conditions include metal complexes such as aluminum complexes of 8-hydroxyquinoline (Japanese Patent Laid-Open No. 59-194393), metal complexes of 10-hydroxybenzo [h] quinoline, oxadiazole derivatives, di- Styryl biphenyl derivative, silole derivative, 3- or 5-hydroxyflavone metal complex, benzoxazole metal complex, benzothiazole metal complex, trisbenzimidazolylbenzene (US Pat. No. 5,645,948), quinoxaline compound No. 207169), phenanthroline derivatives (Japanese Patent Laid-Open No. 5-331459), 2-t-butyl-9,10-N, N′-dicyanoanthraquinonediimine, n-type hydrogenated amorphous silicon carbide, n-type sulfide Examples include zinc and n-type zinc selenide.

  The lower limit of the thickness of the electron transport layer 7 is usually 1 nm, preferably about 5 nm, and the upper limit is usually about 300 nm, preferably about 100 nm. The electron transport layer 7 is formed by laminating on the light emitting layer 5 by a wet film forming method or a vacuum deposition method in the same manner as the hole injection layer 3. Usually, a vacuum deposition method is used.

[8] Electron Injection Layer The electron injection layer 8 serves to efficiently inject electrons injected from the cathode 9 into the light emitting layer 5. In order to perform electron injection efficiently, the material for forming the electron injection layer 8 is preferably a metal having a low work function, and an alkali metal such as sodium or cesium, or an alkaline earth metal such as barium or calcium is used. The thickness of the electron injection layer 8 is preferably 0.1 nm to 5 nm.

Also, an ultrathin insulating film (0.1 to 5 nm) such as LiF, MgF ₂ , Li ₂ O, Cs ₂ CO ₃ may be inserted at the interface between the cathode 9 and the light emitting layer 5 or the electron transport layer 7 described later. This is an effective method for improving the efficiency of the device (Appl. Phys. Lett., 70, 152, 1997; Japanese Patent Laid-Open No. 10-74586; IEEE Trans. Electron. Devices, 44, 1245, 1997). Year; SID 04 Digest, page 154).

  Furthermore, an organic electron transport material represented by a metal complex such as a nitrogen-containing heterocyclic compound such as bathophenanthroline or an aluminum complex of 8-hydroxyquinoline is doped with an alkali metal such as sodium, potassium, cesium, lithium, rubidium ( As described in JP-A-10-270171, JP-A-2002-1000047, JP-A-2002-1000048, and the like, it is possible to improve electron injection / transport properties and achieve excellent film quality. preferable. The film thickness in this case is usually 5 nm or more, preferably 10 nm or more, and usually 200 nm or less, preferably 100 nm or less.

The electron injection layer 8 is formed by laminating on the light emitting layer 5 by the wet film forming method or the vacuum deposition method in the same manner as the light emitting layer 5. In the case of the vacuum vapor deposition method, the vapor deposition source is put in a crucible or metal boat installed in a vacuum vessel, and the inside of the vacuum vessel is evacuated to about 10 ⁻⁴ Pa with an appropriate vacuum pump, and then the crucible or metal boat is By heating and evaporating, the electron injection layer 8 is formed on the substrate placed facing the crucible or the metal boat.

The alkali metal is deposited using an alkali metal dispenser in which nichrome is filled with an alkali metal chromate and a reducing agent. By heating the dispenser in a vacuum container, the alkali metal chromate is reduced and the alkali metal is evaporated. In the case of co-evaporating the organic electron transport material and the alkali metal, the organic electron transport material is put in a crucible installed in a vacuum vessel, and the inside of the vacuum vessel is evacuated to about 10 ⁻⁴ Pa with a suitable vacuum pump. Each crucible and dispenser are simultaneously heated and evaporated to form an electron injection layer 8 on the substrate placed facing the crucible and dispenser. At this time, co-evaporation is uniformly performed in the film thickness direction of the electron injection layer 8, but there may be a concentration distribution in the film thickness direction. The electron injection layer 8 may be omitted.

[9] Cathode The cathode 9 plays a role of injecting electrons into a layer (such as the electron injection layer 8 or the light emitting layer 5) on the light emitting layer 5 side. The material used for the cathode 9 can be the material used for the anode 2, but a metal having a low work function is preferable for efficient electron injection, and tin, magnesium, indium, calcium, A suitable metal such as aluminum or silver or an alloy thereof is used. Specific examples include low work function alloy electrodes such as magnesium-silver alloy, magnesium-indium alloy, and aluminum-lithium alloy.

  The film thickness of the cathode 9 is usually the same as that of the anode 2. For the purpose of protecting the cathode made of a low work function metal, further laminating a metal layer having a high work function and stable to the atmosphere on the cathode increases the stability of the device. For this purpose, metals such as aluminum, silver, copper, nickel, chromium, gold, platinum are used.

[10] Other Constituent Layers Although the above description has focused on the element having the layer structure shown in FIG. 1, in the present embodiment, between the anode 2 and the cathode 9 and the light emitting layer 5 in the organic electroluminescent device. May have any layer as long as its performance is not impaired, and any layer other than the light emitting layer 5 may be omitted. For example, the electron transport layer 7 and the hole blocking layer 6 may be appropriately provided as necessary. 1) Only the electron transport layer 7 2) Only the hole blocking layer 6 3) Hole blocking layer 6 / electron There are usages such as stacking of the transport layer 7, 4) not using, and the like.

  For the same purpose as the hole blocking layer 6, it is also effective to provide an electron blocking layer (not shown) between the hole injection layer 3 and the light emitting layer 5. The electron blocking layer prevents electrons moving from the light emitting layer 5 from reaching the hole injection layer 3, thereby increasing the recombination probability with holes in the light emitting layer 5, and generating generated excitons. There is a role of confining in the light emitting layer 5 and a role of efficiently transporting holes injected from the hole injection layer 3 in the direction of the light emitting layer 5.

The characteristics required for the electron blocking layer include high hole transportability, a large energy gap (difference between HOMO and LUMO), and a high excited triplet level (T1). In the present embodiment, it is preferable that the light emitting layer 5 is formed by a wet film forming method, and in that case, it is preferable that the electron blocking layer is also formed by a wet film forming method because the device manufacturing becomes easy. .
For this reason, it is preferable that the electron blocking layer also has wet film formation compatibility. As a material used for such an electron blocking layer, for example, a copolymer of dioctylfluorene and triphenylamine typified by F8-TFB is used. (Described in WO 2004/084260).

Note that the structure opposite to that shown in FIG. 1, that is, the cathode 9, the electron injection layer 8, the light emitting layer 5, the hole injection layer 3, and the anode 2 can be laminated on the substrate 1 in this order. It is also possible to provide an organic electroluminescent device between two substrates, at least one of which is highly transparent.
Furthermore, a structure in which a plurality of layers shown in FIG. 1 are stacked (a structure in which a plurality of light emitting units are stacked) may be employed. In that case, instead of the interfacial layer (between the light emitting units) (when the anode is ITO and the cathode is Al, the two layers), for example, V ₂ O ₅ is used as the charge generation layer (CGL). This is more preferable from the viewpoint of light emission efficiency and driving voltage.

The organic electroluminescent light emitting device to which the present embodiment is applied is applicable to any of a single device, a device having a structure arranged in an array, and a structure in which an anode and a cathode are arranged in an XY matrix. can do.
The organic electroluminescent light emitting device to which this embodiment is applied can be applied to color display applications having a large area such as a color display module substrate, a color display display device, and a color display television.

  Next, the present invention will be described more specifically with reference to examples. In addition, this invention is not limited to a following example, unless the summary is exceeded.

(Examples 1 to 24, Comparative Examples 1 and 2)
In the organic electroluminescent device shown in FIG. 1, an organic electroluminescent device having a structure not having the hole transport layer 4 was produced by the following method.
An indium tin oxide (ITO) transparent conductive film deposited on a glass substrate 1 having a thickness of 150 nm (sputtered film; sheet resistance: 15Ω) is patterned into a 2 mm wide stripe using normal photolithography and hydrochloric acid etching. Thus, an anode 2 was formed.
The patterned ITO substrate was cleaned in the order of ultrasonic cleaning with acetone, water with pure water, and ultrasonic cleaning with isopropyl alcohol, dried with nitrogen blow, and finally subjected to ultraviolet ozone cleaning.

  The hole injection layer 3 was formed by a wet film forming method as follows. As a material for the hole injection layer 3, a polymer compound having an aromatic amino group having the following structural formula (P-1 (weight average molecular weight: 29400, number average molecular weight: 12600)) and an electron having the structural formula shown below are used. Using the accepting compound (A1), spin coating was performed under the following conditions.

(Spin coating conditions)
Solvent Ethyl benzoate Coating solution concentration P-1 2.0% by weight
A-1 0.4% by weight
Spinner speed 1500rpm
Spinner rotation time 30 seconds Drying conditions 230 ° C. × 15 minutes A uniform thin film having a thickness of 30 nm was formed by the above spin coating.

Then, the light emitting layer 5 was formed by the wet film forming method as follows. The blue fluorescent compound (A) and the blue fluorescent compound (B) described in Table 1 below were added to a toluene solvent so that the weight ratio (A / B) shown in Table 1 and the total concentration was 2% by weight, 25 The coating solution (organic electroluminescent layer coating solution) was prepared by stirring for 10 minutes with an ultrasonic stirring device (Bransonic UL Transonics Corp. 2510J-DTH) at ° C.
Next, this coating solution was spin-coated on the hole injection layer 3 so as to have a dry film thickness of 30 nm and dried at 10 ° C. for 15 minutes to form the light emitting layer 5.

Here, the solubility with respect to the toluene solvent of a blue fluorescent compound (A) and a blue fluorescent compound (B) was evaluated as follows.
Collect 5 mg, 10 mg, 20 mg, and 100 mg of each blue fluorescent compound (A, B) in a 5 ml glass sample bottle, add a toluene solution to each sample bottle, and add the blue fluorescent compound (A, B) and toluene together. Was adjusted to 10 g. Next, this toluene solution was stirred with an ultrasonic stirrer at 25 ° C. for 10 minutes, and the solubility of the blue fluorescent compound (A, B) was evaluated based on the following criteria.
A: 100 mg or more of the blue fluorescent compound was dissolved.
B: 20 to 100 mg of the blue fluorescent compound was dissolved.
C: Blue fluorescent compound of 10 mg or more and less than 20 mg was dissolved.
D: 5 mg or more and less than 10 mg of the blue fluorescent compound was dissolved.

Next, a pyridine derivative (HB-1) shown below was laminated as a hole blocking layer 6 at a crucible temperature of 275 ° C. to 271 ° C. with a deposition rate of 0.1 nm / second and a film thickness of 5 nm. The degree of vacuum at the time of vapor deposition was 4.5 × 10 ⁻⁵ Pa.

Subsequently, an aluminum 8-hydroxyquinoline complex (ET-1) shown below was deposited as an electron transport layer 7 on the hole blocking layer 6 in the same manner. At this time, the crucible temperature of the aluminum 8-hydroxyquinoline complex is controlled in the range of 243 ° C. to 268 ° C., the degree of vacuum during the deposition is 4.6 × 10 ⁻⁵ Pa, and the deposition rate is 0.08 nm / second to 0. The film thickness was 30 nm at 1 nm / second.

  In addition, the substrate temperature at the time of vacuum-depositing said light emitting layer 5, the hole-blocking layer 6, and the electron carrying layer 7 was kept at room temperature.

Here, the element formed up to the electron transport layer 7 was once taken out from the vacuum deposition apparatus into the atmosphere. Next, a stripe shadow mask having a width of 2 mm was brought into close contact with the element so as to be orthogonal to the ITO stripe of the anode 2 as a mask for cathode vapor deposition. Subsequently, this element was placed in another vacuum deposition apparatus, and evacuated until the degree of vacuum in the vacuum deposition apparatus was 2.9 × 10 ⁻⁴ Pa or less, as in the case where the organic layer was formed.

Next, using a molybdenum boat, lithium fluoride (LiF) is deposited at a deposition rate of 0.008 nm / second to 0.01 nm / second, a degree of vacuum of 2.9 × 10 ⁻⁴ Pa, and a film thickness of 0.5 nm. A film was formed as an electron injection layer 8 on the electron transport layer 7. Subsequently, similarly, the aluminum was heated by a molybdenum boat, the film thickness at a deposition rate of 0.08 nm / sec ～0.1Nm / sec, the degree of vacuum ^{2.7 × 10 -4 Pa~2.5 × 10 -4} Pa The cathode 9 was completed by forming an aluminum layer of 80 nm. When forming the above electron injection layer 8 and the cathode 9, the substrate temperature at the time of vapor deposition was kept at room temperature.

As described above, an organic electroluminescent light emitting device having a light emitting area portion having a size of 2 mm × 2 mm was prepared.
The presence or absence of light emission and the color of light emitted when a voltage of 7 V was applied to the device were evaluated. In addition, the glass transition temperature (Tg) of the blue fluorescent compound (A, B) was measured with a differential scanning calorimeter (manufactured by SII Nanotechnology Inc .: DSC6220). The results of Examples 1 to 17 and Comparative Examples 1 and 2 are shown in Table 5, and the results of Examples 18 to 24 are shown in Table 6.

  The structural formulas of the blue fluorescent compounds (A, B) in Tables 5 and 6 are shown below.

From the results shown in Table 5 and Table 6, a coating solution (organic electric field) containing a blue fluorescent compound (A, B) having a glass transition temperature (Tg) of 100 ° C. or higher and a solubility in toluene of 0.2 wt% or higher. The light emitting layer of the organic electroluminescent device can be formed by spin coating using the fluorescent light emitting layer coating solution.
Using this coating solution, it is easily estimated that a light emitting layer can be formed in the same manner as the spin coating method by various printing coating methods such as an ink jet coating method and a screen printing coating method.

(Example 25)
An organic electroluminescent device was produced in the same manner as in Example 22 except that the drying condition after spin coating of the hole injection layer was changed to 230 ° C. for 1 hour. The light emission characteristics of this device are shown in Table 7. The light emission characteristics are shown as relative values when the element manufactured in Example 22 is 1.

(Example 26)
An organic electroluminescent device was produced in the same manner as in Example 22 except that the drying condition after spin coating of the hole injection layer was changed to 230 ° C. for 12 hours. The light emission characteristics of this device are shown in Table 7. The light emission characteristics are shown as relative values when the element manufactured in Example 22 is 1.

(Example 27)
An organic electroluminescent device was produced in the same manner as in Example 22 except that drying after spin coating when forming the light emitting layer was performed in a nitrogen atmosphere having an oxygen concentration of 1 ppm or less and a water concentration of 1 ppm or less. The light emission characteristics of this device are shown in Table 7. The light emission characteristics are shown as relative values when the element manufactured in Example 22 is 1.

(Example 28)
An organic electroluminescent light emitting device was produced in the same manner as in Example 22 except that 3% by weight of the following compound (H-1) was added to the coating solution for forming the light emitting layer with respect to the blue fluorescent compound. The light emission characteristics of this device are shown in Table 7. The light emission characteristics are shown as relative values when the element manufactured in Example 22 is 1.

(Example 29)
An organic electroluminescent device was produced in the same manner as in Example 22 except that 3% by weight of the following compound (H-2) was added to the coating solution for forming the light emitting layer with respect to the blue fluorescent compound. The light emission characteristics of this device are shown in Table 7. The light emission characteristics are shown as relative values when the element manufactured in Example 22 is 1.

(Example 30)
Solubility in toluene and the following eight types of compounds (3-1) to (3-8) exemplified as specific examples of the 9,10-substituted anthracene compound (bianthracene compound) represented by the above formula (3) The glass transition temperature was measured. The results are shown in Table 8.

(Example 31)
With respect to the compounds (9-1) and (9-2) having the following aliphatic rings, solubility in toluene and glass transition temperature were measured. The results are shown in Table 9. In addition, any compound had a blue color tone when the compound was formed on a glass substrate under the following conditions.

(Example 32)
In accordance with the following operation, an organic electroluminescent device having a light emitting area of 2 mm × 2 mm was prepared.
(Formation of anode)
An indium tin oxide (ITO) transparent conductive film was formed on a glass substrate with a thickness of 150 nm (sputtered film product, sheet resistance 15Ω). This transparent conductive film was patterned into a stripe having a width of 2 mm by an ordinary photolithography technique to form an anode.
The patterned ITO substrate was cleaned in the order of ultrasonic cleaning with acetone, water with pure water, and ultrasonic cleaning with isopropyl alcohol, and then dried with nitrogen blow to perform ultraviolet ozone cleaning.

(Formation of hole injection layer)
Subsequently, a hole injection layer was formed on the anode. As a material for the hole injection layer, a non-conjugated polymer compound (PB-1: weight average molecular weight 29,400, number average molecular weight 12,600) having an aromatic amino group having the structural formula shown below is used, and photoreaction is performed. It spin-coated on the anode with the initiator (A-1).
Table 10 shows the spin coating conditions. Moreover, the use ratio of the non-conjugated polymer compound (PB-1) and the photoreaction initiator (A-1) was (PB-1) :( A-1) = 10: 4 (weight ratio). After spin coating, drying was performed at 260 ° C. for 180 minutes to form a uniform hole injection layer thin film having a thickness of 30 nm.

(Hole transport layer)
A hole transport layer was formed on the formed hole injection layer. A hole transport layer was formed by spin coating using the following compound (HT-1) as a material for the hole transport layer.
Table 11 shows the spin coating conditions. After spin coating, drying was performed at 230 ° C. for 60 minutes to form a uniform hole transport layer thin film having a thickness of 20 nm.

(Light emitting layer)
Next, a light emitting layer was formed on the formed hole transport layer. As a material for the light emitting layer, a light emitting layer was formed by spin coating using a composition in which the following compound 1 and a fluorescent light emitting dopant (9-2) were dissolved in toluene under the following conditions.
Table 12 shows the spin coating conditions. Moreover, the usage-ratio of the compound 1 and (9-2) was made into the compound 1: (9-2) = 10: 1 (weight ratio).
After spin coating, drying was performed at 100 ° C. for 60 minutes to form a uniform light emitting layer thin film having a thickness of 50 nm. The solubility of Compound 1 was 8%.

(Hole blocking layer / electron transport layer)
Subsequently, a hole blocking layer was formed on the formed light emitting layer, and an electron transport layer was further formed on the hole blocking layer.
A hole blocking layer having a thickness of 10 nm was formed by vacuum deposition using HB-1 shown below as a material for the hole blocking layer.
Next, an electron transport layer having a film thickness of 30 nm was formed by vacuum deposition using ET-1 shown below as a material for the electron transport layer.

(Electron injection layer / cathode)
Next, an electron injection layer 8 was formed on the electron transport layer, and a cathode was formed on the electron injection layer 8. As the electron injection layer 8, lithium fluoride (LiF) was used, and the electron injection layer 8 having a film thickness of 0.5 nm was formed by a vacuum evaporation method in the same manner as the organic layer. Also, aluminum was used as the cathode material, and cathodes with a film thickness of 80 nm were stacked in a 2 mm-wide stripe shape that was orthogonal to the ITO stripe that was the anode.
As described above, an organic electroluminescent light emitting device having a light emitting area portion having a size of 2 mm × 2 mm was obtained. Blue light emission was obtained from this organic electroluminescence device.

(Example 33)
An organic electroluminescent device having the structure shown in FIG. 1 was produced by the following method.
An indium tin oxide (ITO) transparent conductive film deposited on a glass substrate 1 having a thickness of 150 nm (sputtered film product: sheet resistance 15 Ω) is 2 mm wide using ordinary photolithography technology and hydrochloric acid etching. The anode 2 was formed by patterning into a stripe.
The patterned ITO substrate was cleaned in the order of ultrasonic cleaning with acetone, water with pure water, and ultrasonic cleaning with isopropyl alcohol, dried with nitrogen blow, and finally subjected to ultraviolet ozone cleaning.
The hole injection layer 3 was formed by a wet film forming method as follows. As a material for the hole injection layer 3, a polymer compound having an aromatic amino group having the following structural formula (P-1 (weight average molecular weight: 29400, number average molecular weight: 12600)) and an electron having the structural formula shown below are used. Using the accepting compound (A-1), spin coating was performed under the following conditions.

(Spin coating conditions)
Solvent Ethyl benzoate Coating solution concentration (P-1) 2.0% by weight
(A-1) 0.4% by weight
Spinner speed 1500rpm
Spinner rotation time 30 seconds Drying conditions 230 ° C x 15 minutes

A uniform thin film having a thickness of 30 nm was formed by the above spin coating.
Subsequently, the hole transport layer 4 was formed by a wet film forming method as follows. The hole transport layer 4 was formed by spin coating using the following compound (HT-2) as a material for the hole transport layer 4. After spin coating, drying was performed in nitrogen at 230 ° C. for 60 minutes to form a uniform hole transport layer 4 thin film having a thickness of 20 nm.

(Spin coating conditions)
Solvent Toluene Solid concentration 0.5% by weight
Spinner speed 1500rpm
Spinner rotation time 30 seconds Atmosphere Nitrogen

  Then, the light emitting layer 5 was formed by the wet film forming method as follows. The blue fluorescent compound (10-1) and the blue fluorescent compound (10-2) shown below are weight ratio (10-1) / (10-2) = 5/95, and the total concentration is 2% by weight. Was added to a toluene solvent, and stirred at 25 ° C. for 10 minutes with an ultrasonic stirrer (2510J-DTH manufactured by Bransonic UL Transonics Corp.) to prepare a coating solution (organic electroluminescent layer coating solution).

Next, this coating solution was spin-coated on the hole transport layer 4 so as to have a dry film thickness of 30 nm and dried at 10 ° C. for 15 minutes to form the light emitting layer 5.
Here, the solubility of the blue fluorescent compound (10-1) and the blue fluorescent compound (10-2) in the toluene solvent was such that (10-1) was B (20 mg or more and less than 100 mg of the blue fluorescent compound was dissolved) ), (10-2) was A (100 mg or more of the blue fluorescent compound was dissolved). Moreover, the glass transition temperature of (10-2) was 148 degreeC.

Next, a pyridine derivative (HB-1) shown below as the hole blocking layer 6 was laminated at a crucible temperature of 275 ° C. to 271 ° C. with a deposition rate of 0.1 nm / second and a film thickness of 5 nm. The degree of vacuum at the time of vapor deposition was 4.5 × 10 ⁻⁵ Pa.

Subsequently, the following aluminum complex (ET-2) was deposited as an electron transport layer 7 on the hole blocking layer 6 in the same manner. The crucible temperature of the aluminum complex at this time is controlled in the range of 243 ° C. to 268 ° C., the degree of vacuum during the deposition is 4.6 × 10 ⁻⁵ Pa, and the deposition rate is 0.08 nm / second to 0.1 nm / second. The film thickness was 30 nm.

In addition, the substrate temperature at the time of vacuum-depositing said light emitting layer 5, the hole-blocking layer 6, and the electron carrying layer 7 was kept at room temperature.
Here, the element formed up to the electron transport layer 7 was once taken out from the vacuum deposition apparatus into the atmosphere. Next, a stripe shadow mask having a width of 2 mm was brought into close contact with the element so as to be orthogonal to the ITO stripe of the anode 2 as a mask for cathode vapor deposition. Subsequently, this element was placed in another vacuum deposition apparatus, and evacuated until the degree of vacuum in the vacuum deposition apparatus was 2.9 × 10 ⁻⁴ Pa or less, as in the case where the organic layer was formed.
Next, lithium fluoride (LiF) was used as the electron injection layer 8 by using a molybdenum boat at a deposition rate of 0.008 nm / second to 0.01 nm / second at a vacuum degree of 2.9 × 10 ⁻⁴ Pa. A film having a thickness of 5 nm was formed on the electron transport layer 7. Subsequently, similarly, the aluminum was heated by a molybdenum boat, the film thickness at a deposition rate of 0.08 nm / sec ～0.1Nm / sec, the degree of vacuum ^{2.7 × 10 -4 Pa~2.5 × 10 -4} Pa The cathode 9 was completed by forming an aluminum layer of 80 nm. When forming the above electron injection layer 8 and the cathode 9, the substrate temperature at the time of vapor deposition was kept at room temperature.

As described above, an organic electroluminescent device having a light emitting area portion having a size of 2 mm × 2 mm was prepared. When a voltage of 7 V was applied to the organic electroluminescent light emitting device, a blue light emitting color was exhibited. The light emission characteristics of the organic electroluminescent light emitting device with the light emitting characteristics of the organic electroluminescent light emitting device prepared in Example 22 as 1 were as follows.
Luminance 3
Luminous efficiency 4
Drive voltage (1/2)
Life 5>

It is a cross-sectional schematic diagram which shows the structural example suitable for an organic electroluminescent light emitting element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Anode, 3 ... Hole injection layer, 4 ... Hole transport layer, 5 ... Light emitting layer, 6 ... Hole blocking layer, 7 ... Electron transport layer, 8 ... Electron injection layer, 9 ... Cathode

Claims (8)

An organic electroluminescent light emitting device having a light emitting layer containing a light emitting compound between a pair of electrodes,
The luminescent compound is:
It is composed of a blue fluorescent compound having a glass transition temperature (Tg) of 100 ° C. or higher and a solubility in toluene of 0.2% by weight or higher, and the blue fluorescent compound is represented by the following formula (3) having at least an anthracene skeleton. a luminescent compound, viewed including the other light-emitting compound represented by the following formula (1) having a structure other than the anthracene skeleton, a,
The blue fluorescent compound is
At least a binuclear or trinuclear fused ring (KK1);
Having 3 to 5 condensed rings (KK2),
The difference between the number of KK2 nuclei and the number of KK1 nuclei is 1 or more and 3 or less .

(In Formula (3), R ₉ and R ₁₀ each independently represents an aromatic hydrocarbon group which may have a substituent.)

(In formula (1), R _{1 to} R ₄ each independently represents an aromatic condensed ring group.) 2. The organic electroluminescent device according to claim 1 , wherein the anthracene skeleton of the blue fluorescent compound has a substituent that is unsubstituted at the 2-position and includes at least 5 benzene rings at the 6-position. The light-emitting layer, the blue fluorescent compound and a predetermined organic electroluminescent fluorescent light-emitting device according to claim 1 or 2, characterized in coating solution to be formed by a coating containing an organic solvent. 2. The light emitting layer is formed by applying a coating solution containing the blue fluorescent compound and a predetermined organic solvent, and then dried in an environment having an oxygen concentration of 1 ppm or less and a moisture concentration of 1 ppm or less. 4. The organic electroluminescence device according to any one of items 1 to 3 . A hole injection layer formed by a wet film forming method is further provided between the light emitting layer and the electrode, and the hole injection layer is a layer heated at 200 ° C. or more. Item 5. The organic electroluminescent light emitting device according to any one of Items 1 to 4 . An organic electroluminescent light emitting layer coating solution containing a luminescent compound and a predetermined organic solvent,
The luminescent compound is:
It is composed of a blue fluorescent compound having a glass transition temperature (Tg) of 100 ° C. or higher and a solubility in toluene of 0.2% by weight or higher, and the blue fluorescent compound is represented by the following formula (3) having at least an anthracene skeleton. a luminescent compound, viewed including the other light-emitting compound represented by the following formula (1) having a structure other than the anthracene skeleton, a,
The blue fluorescent compound is
At least a binuclear or trinuclear fused ring (KK1);
Having 3 to 5 condensed rings (KK2),
The organic electroluminescent light emitting layer coating solution , wherein the difference between the number of KK2 nuclei and the number of KK1 nuclei is 1 or more and 3 or less .

(In Formula (3), R ₉ and R ₁₀ each independently represents an aromatic hydrocarbon group which may have a substituent.)

(In formula (1), R _{1 to} R ₄ each independently represents an aromatic condensed ring group.) The organic electroluminescent light emitting layer coating according to claim 6 , wherein the anthracene skeleton of the blue fluorescent compound has a substituent which is unsubstituted at the 2-position and includes at least 5 benzene rings at the 6-position. solution. Color display the display device, characterized in that it comprises an organic electroluminescent fluorescent light-emitting device according to any one of claims 1 to 5.

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