JP5402703B2 - Organic electroluminescence device, organic EL display, organic EL lighting, and organic EL signal device - Google Patents

Description

  The present invention relates to an organic electroluminescent element, and an organic EL display, an organic EL illumination, and an organic EL signal device including the same.

In recent years, organic electroluminescent elements have been actively developed as light emitting devices such as displays and lighting. This organic electroluminescent element injects positive and negative charges into an organic thin film between electrodes and takes out an excited state generated by recombination as light.
Organic electroluminescent devices that are currently in practical use are generally produced using a technique in which a relatively low molecular weight compound is heated under high vacuum conditions and vapor-deposited on an upper substrate. This method is used for small and medium-sized displays that have been put to practical use. Further, by adjusting the film thickness of the organic compound layer between the electrodes, it is possible to select the optical path length suitable for the emission wavelength, and it is possible to optimize the emission of each color of RGB. However, this vacuum evaporation method is difficult to uniformly deposit on a large area substrate and is not suitable for manufacturing a large display. Moreover, the utilization efficiency of the organic material which is a vapor deposition source is low, and there also exists a problem that manufacturing cost is high because the frequency | count of coating with a mask increases.

  On the other hand, as a means for producing these large-area organic EL panels, a method for producing an organic EL panel by a wet film formation method typified by a spin coating method, an ink jet method, a dip coating method, various printing methods and the like has been proposed. Yes. Although these methods are said to be advantageous in terms of cost compared to vacuum deposition methods, satisfying the various performances required for organic electroluminescent displays such as low voltage drive, high efficiency, and long lifetime is a single layer wet process. Difficult in film formation. Therefore, the multilayer lamination technique by wet film formation is very important in aiming at high performance of the coating type organic electroluminescence device.

  Patent Document 1 and Non-Patent Document 1 disclose organic electroluminescent elements that realize multilayer stacking by wet film formation. However, there remains a problem with the driving life.

Japanese Patent Laid-Open No. 2004-199935

Adv. Materials 18,948 (2006)

  An object of the present invention is to provide an organic electroluminescent device having a low driving voltage, high luminous efficiency, and long driving life in an organic electroluminescent device including at least one organic layer formed by a wet film-forming method. To do.

As a result of intensive studies by the present inventors, the ratio of the hole mobility and the electron mobility of the light emitting layer is set to a certain value or more, and the hole mobility or charge mobility of the organic layer adjacent to the light emitting layer is increased. The inventors have found that the above-mentioned problems can be solved by setting the value to a certain value or more, and have reached the present invention.
That is, the present invention is an organic electroluminescent device comprising an anode, a first organic layer, a light-emitting layer, a second organic layer, and a cathode in this order, and the first organic layer or the light-emitting layer is a wet component. An organic electroluminescent element formed by a film method and satisfying the following formulas (1), (2) and (3), and an organic EL display, an organic EL illumination and an organic EL signal each including the organic electroluminescent element Exists in the device.

μ (h1) / μ (e1) ≧ 5 (1)
μ (h2) ≧ 1.0 × 10 ⁻⁴ (2)
μ (e2) ≧ 1.0 × 10 ⁻⁴ (3)
(In the above formula, μ (h1) is the hole mobility (cm ² / V · s) of the light emitting layer,
μ (e1) is the electron mobility (cm ² / V · s) of the light emitting layer,
μ (h2) is the hole mobility (cm ² / V · s) of the first organic layer,
μ (e2) is the electron mobility (cm ² / V · s) of the second organic layer,
Represents. The charge mobility is a value obtained when the square root of the electric field strength is 500 (V / cm) ^0.5 . )

It is sectional drawing which shows typically an example of the structure of the organic electroluminescent element of this invention.

Embodiments of the organic electroluminescent element, organic EL display, organic EL lighting, and organic EL signal device of the present invention will be described in detail. The description of the constituent elements described below is an example of the embodiment of the present invention (representative) The present invention is not specified in these contents unless it exceeds the gist.
The present invention is an organic electroluminescent device comprising an anode, a first organic layer, a light emitting layer, a second organic layer, and a cathode in this order, and the first organic layer or the light emitting layer is formed by a wet film formation method. An organic electroluminescent element, and an organic EL display, an organic EL illumination, and an organic EL signal device including the organic electroluminescent element, characterized by satisfying the following formulas (1), (2), and (3): Exist.

μ (h1) / μ (e1) ≧ 5 (1)
μ (h2) ≧ 1.0 × 10 ⁻⁴ (2)
μ (e2) ≧ 1.0 × 10 ⁻⁴ (3)
(In the above formula, μ (h1) is the hole mobility (cm ² / V · s) of the light emitting layer,
μ (e1) is the electron mobility (cm ² / V · s) of the light emitting layer,
μ (h2) is the hole mobility (cm ² / V · s) of the first organic layer,
μ (e2) is the electron mobility (cm ² / V · s) of the second organic layer,
Represents. The charge mobility is a value obtained when the square root of the electric field strength is 500 (V / cm) ^0.5 . )

<Organic layer>
In the present invention, the “organic layer” refers to a layer containing an organic compound.
In the organic electroluminescent element of the present invention, the organic layer refers to each layer disposed between the anode and the cathode.
Examples of the organic layer in the organic electroluminescence device of the present invention include a hole injection layer, a hole transport layer, a light emitting layer, a hole blocking layer, an electron transport layer, and an electron injection layer.

[1. First organic layer]
The 1st organic layer in this invention is an organic layer which has between an anode and a light emitting layer. When two or more layers are included between the anode and the light emitting layer, the layer adjacent on the anode side of the light emitting layer is defined as the first organic layer.

The hole mobility μ (h2) of the first organic layer in the present invention is described in [5. Charge mobility] (
When measured by the method described in the section of “Measurement method of charge mobility”, it is usually 1.0 × 10 ⁻⁴ cm ² / V · s or more, preferably 1.2 × 10 ⁻⁴ cm ² / V · s or more. Moreover, it is 1.5 * 10 < ^-4 > cm < ² > / V * s or less normally.
Within this range, the hole injecting property to the light emitting layer is good, and the organic electroluminescent element can be driven with a low driving voltage.
The first organic layer is preferably a layer containing a hole transporting compound.

(1-1. Compound)
The hole transporting compound may be a monomer (a compound having a single molecular weight) or an oligomer (a low molecular weight polymer compound having a repeating unit), or a polymer (a high molecular weight polymer compound having a repeating unit). ). The hole transporting compound is preferably a polymer compound having a repeating unit such as an oligomer or a polymer because it is excellent in film formability or heat resistance.

(1-1-1. Molecular weight)
When the hole transporting compound is a monomer, the molecular weight is usually 5000 or less, preferably 2500 or less, preferably 300 or more, more preferably 500 or more. If the molecular weight exceeds this upper limit, purification may be difficult due to the high molecular weight of impurities, and if the molecular weight is lower than this lower limit, the glass transition temperature, melting point, vaporization temperature, etc. will decrease, so heat resistance will be reduced. It may be severely damaged.

When the hole transporting compound is an oligomer or a polymer, its weight average molecular weight is usually 3,000,000 or less, preferably 1,000,000 or less, more preferably 500,000 or less, and usually 1 5,000 or more, preferably 2,500 or more, more preferably 5,000 or more.
Within the above range, it is preferable from the viewpoint that it is difficult to increase the molecular weight of impurities, the purification is easy, the glass transition temperature, the melting point and the vaporization temperature are high, and the heat resistance is excellent.

When the hole transporting compound is an oligomer or a polymer, its dispersity Mw / Mn (Mw: weight average molecular weight, Mn: number average molecular weight) is usually 3.0 or less, preferably 2.5 or less, more preferably. Is 2.0 or less, preferably 1.0 or more, more preferably 1.1 or more, and particularly preferably 1.2 or more.
When the dispersity is within the above range, it is preferable in terms of easy purification, good solubility in a solvent, and excellent film formability.

  In addition, the weight average molecular weight (and number average molecular weight) in this invention is determined by SEC (size exclusion chromatography) measurement. In SEC measurement, the elution time is shorter for higher molecular weight components and the elution time is longer for lower molecular weight components, but using the calibration curve calculated from the elution time of polystyrene (standard sample) with a known molecular weight, the elution time of the sample is changed to the molecular weight. By converting, the weight average molecular weight (and number average molecular weight) is calculated.

(1-1-2. Structure)
The material forming the first organic layer is preferably a material having a high hole transport capability and capable of efficiently transporting injected holes. Therefore, it is preferable that the ionization potential is small, the transparency to visible light is high, the hole mobility is large, the stability is high, and impurities that become traps are not easily generated during manufacturing or use. In many cases, since it is in contact with the light emitting layer, it is preferable not to quench the light emitted from the light emitting layer or to reduce the efficiency by forming an exciplex with the light emitting layer.

Such a material of the first organic layer may be selected from materials conventionally used as a constituent material of the first organic layer. For example, hole transport used in the above-described hole injection layer is used. What was illustrated as an ionic compound is mentioned. In addition, arylamine derivatives, fluorene derivatives, spiro derivatives, carbazole derivatives, pyridine derivatives, pyrazine derivatives, pyrimidine derivatives, triazine derivatives, quinoline derivatives, phenanthroline derivatives, phthalocyanine derivatives, porphyrin derivatives, silole derivatives, oligothiophene derivatives, condensed polycyclic aromatics Group derivatives, metal complexes and the like.

  In addition, for example, polyvinylcarbazole derivatives, polyarylamine derivatives, polyvinyltriphenylamine derivatives, polyfluorene derivatives, polyarylene derivatives, polyarylene ether sulfone derivatives containing tetraphenylbenzidine, polyarylene vinylene derivatives, polysiloxane derivatives, polythiophenes Derivatives, poly (p-phenylene vinylene) derivatives, and the like. These may be any of alternating copolymer compounds, random polymer compounds, block polymer compounds, and graft copolymer compounds. Further, it may be a polymer having a branched main chain and three or more terminal portions, or a so-called dendrimer.

Of these, polyarylamine derivatives and polyarylene derivatives are preferred.
The polyarylamine derivative is preferably a polymer compound containing a repeating unit represented by the following formula (II). In particular, it is preferably a polymer compound composed of a repeating unit represented by the following formula (II). In this case, Ar ^a or Ar ^b may be different in each repeating unit.

(In Formula (II), Ar ^a and Ar ^b each independently represent an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent.)
Examples of the aromatic hydrocarbon group which may have a substituent include, for example, a benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, perylene ring, tetracene ring, pyrene ring, benzpyrene ring, chrysene ring, triphenylene ring, and acenaphthene. Examples thereof include a group derived from a 6-membered monocyclic ring or a 2-5 condensed ring, such as a ring, a fluoranthene ring, and a fluorene ring, and a group in which two or more of these rings are linked by a direct bond.

  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, phenanthridine ring, benzimidazole ring, perimidine ring, quinazoline ring, quinazolinone ring, azulene ring, etc. Or a group and the rings of from 2-4 fused rings include groups formed by connecting a direct bond or two or more rings.

From the viewpoints of solubility and heat resistance, Ar ^a and Ar ^b are each independently selected from the group consisting of a benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, triphenylene ring, pyrene ring, thiophene ring, pyridine ring, and fluorene ring. A group derived from a selected ring or a group formed by linking two or more benzene rings (for example, a biphenyl group or a terphenyl group) is preferable.
Among these, a group derived from a benzene ring (phenyl group), a group formed by connecting two benzene rings (biphenyl group), and a group derived from a fluorene ring (fluorenyl group) are preferable.

Examples of the substituent that the aromatic hydrocarbon group and the aromatic heterocyclic group in Ar ^a and Ar ^b may have include an alkyl group, an alkenyl group, an alkynyl group, an alkoxy group, an aryloxy group, an alkoxycarbonyl group, and a dialkyl. Examples thereof include an amino group, a diarylamino group, an acyl group, a halogen atom, a haloalkyl group, an alkylthio group, an arylthio group, a silyl group, a siloxy group, a cyano group, an aromatic hydrocarbon ring group, and an aromatic heterocyclic group.

As the polyarylene derivative, an arylene group such as an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent exemplified as Ar ^a or Ar ^b in the formula (II) is used as its repeating unit. The high molecular compound which has is mentioned.
As the polyarylene derivative, a polymer compound having a repeating unit composed of the following formula (III-1) and / or the following formula (III-2) is preferable.

(In formula (III-1), R ^a , R ^b , R ^c and R ^d are each independently an alkyl group, an alkoxy group, a phenylalkyl group, a phenylalkoxy group, a phenyl group, a phenoxy group, an alkylphenyl group, Represents an alkoxyphenyl group, an alkylcarbonyl group, an alkoxycarbonyl group, or a carboxy group, and t and s each independently represent an integer of 0 to 3. When t or s is 2 or more, they are contained in one molecule. A plurality of R ^a or R ^b may be the same or different, and adjacent R ^a or R ^b may form a ring.)

(In Formula (III-2), R ^e and R ^f are each independently the same as R ^a , R ^b , R ^c or R ^d in Formula (III-1) above. Independently, it represents an integer of 0 to 3. When r or u is 2 or more, a plurality of R ^e and R ^f contained in one molecule may be the same or different, and adjacent R ^e or R ^f may form a ring, and X represents an atom or a group of atoms constituting a 5-membered ring or a 6-membered ring.)
Specific examples of X include an oxygen atom, a boron atom which may have a substituent, a nitrogen atom which may have a substituent, a silicon atom which may have a substituent, and a substituent. A phosphorus atom which may be substituted, a sulfur atom which may have a substituent, a carbon atom which may have a substituent, or a group formed by bonding these.

  The polyarylene derivative has a repeating unit represented by the following formula (III-3) in addition to the repeating unit represented by the following formula (III-1) and / or the following formula (III-2). Is preferred.

(In the formula (III-3), Ar ^{c to} Ar ^j each independently represents an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent. Independently represents 0 or 1.)
Specific examples of Ar ^{c to} Ar ^j are the same as Ar ^a and Ar ^b in the formula (II).

Specific examples of the above formulas (III-1) to (III-3) and specific examples of polyarylene derivatives include those described in JP-A-2008-98619.
The structure of the hole transporting compound is not particularly limited, but is preferably a compound having a structure represented by the following formula (4) as a partial structure.

  In addition, as a hole transporting compound, a conductive polymer (PEDOT / PSS) obtained by polymerizing 3,4-ethylenedioxythiophene (3,4-ethylenedioxythiophene), a polythiophene derivative, in high molecular weight polystyrene sulfonic acid. Is also preferred. Moreover, the end of this polymer may be capped with methacrylate or the like.

(1-1-4. Insolubilizing group)
The hole transporting compound according to the present invention is preferably a compound having an insolubilizing group. That is, the first organic layer is preferably a layer obtained by insolubilizing a compound having an insolubilizing group.
The insolubilizing group is a group that reacts by irradiation with heat and / or active energy rays, and is a group having an effect of lowering solubility in an organic solvent or water after the reaction than before the reaction.
In the present invention, the insolubilizing group is preferably a dissociating group or a crosslinkable group.

(1-1-4-1. Crosslinkable group)
In addition, the hole transporting compound according to the present invention has a crosslinkable group as an insolubilizing group, and the reaction with respect to the solvent before and after the reaction (insolubilizing reaction) caused by irradiation with heat and / or active energy rays. It is preferable at the point which can make a big difference in solubility.

Here, the crosslinkable group refers to a group that reacts with the same or different groups of other molecules located nearby by irradiation with heat and / or active energy rays to form a new chemical bond.
Examples of the crosslinkable group include groups shown in the crosslinkable group group T in that it is easily insolubilized.
[Crosslinkable group T]

(In formula, R < ¹ > -R < ⁵ > represents a hydrogen atom or an alkyl group each independently. Ar < ³¹ > may have the aromatic hydrocarbon group or substituent which may have a substituent. Represents an aromatic heterocyclic group.)
Groups that are insolubilized by cationic polymerization, such as cyclic ether groups such as epoxy groups and oxetane groups, and vinyl ether groups are preferred because they are highly reactive and easily insolubilized. Among these, an oxetane group is particularly preferable from the viewpoint that the rate of cationic polymerization can be easily controlled, and a vinyl ether group is preferable from the viewpoint that a hydroxyl group that may cause deterioration of the device during the cationic polymerization is hardly generated.

A group that undergoes a cycloaddition reaction, such as an arylvinylcarbonyl group such as a cinnamoyl group, or a group derived from a benzocyclobutene ring, is preferred from the viewpoint of further improving electrochemical stability.
Among the crosslinkable groups, a group derived from a benzocyclobutene ring is particularly preferable in that the structure after insolubilization is particularly stable.
The crosslinkable group may be directly bonded to the aromatic hydrocarbon group or aromatic heterocyclic group in the molecule, but may be bonded via a divalent group. As the divalent group, a group selected from an —O— group, a —C (═O) — group, or an (optionally substituted) —CH ₂ — group may be selected from 1 to 30 in any order. It is preferable to bind to an aromatic hydrocarbon group or an aromatic heterocyclic group via a divalent group formed by connecting them individually.

(1-1-4-2. Dissociation group)
The hole transport material according to the present invention preferably has a dissociation group as an insolubilizing group in terms of excellent charge transport ability after insolubilization (after dissociation reaction).
Here, the dissociating group refers to a group that dissociates from a bonded aromatic hydrocarbon ring at 70 ° C. or more and is soluble in a solvent. Here, being soluble in a solvent means that the compound is dissolved in toluene at 0.1% by weight or more at room temperature in a state before reacting by irradiation with heat and / or active energy rays. The solubility in toluene is preferably 0.5% by weight or more, more preferably 1% by weight or more.

Such a dissociating group is preferably a group that thermally dissociates without forming a polar group on the aromatic hydrocarbon ring side, and more preferably a group that dissociates thermally by a reverse Diels-Alder reaction.
Furthermore, it is preferably a group that thermally dissociates at 100 ° C. or higher, and preferably a group that thermally dissociates at 300 ° C. or lower.

Specific examples of the dissociating group are as follows, but the present invention is not limited thereto.
A specific example in the case where the dissociating group is a divalent group is as shown in <Divalent dissociating group group A> below.
<Divalent dissociation group A>

A specific example in the case where the dissociating group is a monovalent group is as shown in <Monovalent dissociating group B> below.
<Monovalent dissociation group B>

The insolubilizing compound may be any of a monomer, an oligomer, and a polymer, but is preferably a polymer in terms of excellent film formability. The insolubilizing compound may have only 1 type, and may have 2 or more types by arbitrary combinations and ratios.
As the insolubilizing compound, it is preferable to use a hole transporting compound having an insolubilizing group. Examples of the hole transporting compound include those exemplified above, and those in which an insolubilizing group is bonded to the main chain or side chain with respect to these hole transporting compounds. In particular, the insolubilizing group is preferably bonded to the main chain via a linking group such as an alkylene group. In particular, the hole transporting compound is preferably a polymer compound containing a repeating unit having an insolubilizing group, and the insolubilizing group is represented by the above formula (II) or formulas (III-1) to (III-3). A polymer compound having a repeating unit bonded directly or via a linking group is preferred.

As the insolubilizing compound, it is preferable to use a hole transporting compound having an insolubilizing group.
Examples of hole transporting compounds include nitrogen-containing aromatic compound derivatives such as pyridine derivatives, pyrazine derivatives, pyrimidine derivatives, triazine derivatives, quinoline derivatives, phenanthroline derivatives, carbazole derivatives, phthalocyanine derivatives, porphyrin derivatives; triphenylamine derivatives Silole derivatives; oligothiophene derivatives, condensed polycyclic aromatic derivatives, metal complexes and the like. Among them, nitrogen-containing aromatic derivatives such as pyridine derivatives, pyrazine derivatives, pyrimidine derivatives, triazine derivatives, quinoline derivatives, phenanthroline derivatives, carbazole derivatives; triphenylamine derivatives, silole derivatives, condensed polycyclic aromatic derivatives, metal complexes, etc. In particular, a triphenylamine derivative, that is, a compound having a structure represented by the formula (4) as a partial structure is more preferable.

(1-1-5. Specific example)
Specific examples of the hole transporting compound in the present invention are shown below, but the present invention is not limited thereto.
<Specific examples of hole transporting compounds>

(1-1-6. Other components)
The first organic layer may contain other components as long as the effects of the present invention are not impaired. Examples of other components include various electron-accepting compounds, light emitting materials, binder resins, leveling agents, coating properties improving agents such as antifoaming agents, and the like. In addition, only 1 type may be used for another component, and 2 or more types may be used together in the combination and ratio of simmering.
When the organic layer is a single layer between the anode and the light emitting layer, that is, only the first organic layer, it is preferable that the first organic layer contains an electron-accepting compound described later.

(1-2. Composition)
When the first organic layer is formed by a wet film formation method, the hole transporting compound constituting the first organic layer and, if necessary, other components are mixed with an appropriate solvent for film formation. A composition (first organic layer forming composition) is prepared and used.

The content of the hole transporting compound in the first organic layer forming composition is usually 0.1% by weight or more, preferably 0.5% by weight or more, usually 50% by weight or less, preferably 20% by weight or less. It is. In addition, 2 or more types of hole transportable compounds may be contained in the 1st composition for organic layer formation, In that case, it is preferable that the sum total of 2 or more types becomes said range.
The first composition for forming an organic layer according to the present invention usually contains a solvent.

Although it does not restrict | limit especially as a solvent contained in the 1st composition for organic layer formation concerning this invention, The said hole transportable compound is 0.1 weight% normally, Preferably it is 0.5. A solvent that dissolves by weight%, more preferably 1.0 weight% or more.
The boiling point of the solvent is usually 110 ° C. or higher, preferably 140 ° C. or higher, particularly 200 ° C. or higher, usually 400 ° C. or lower, and preferably 300 ° C. or lower. If the boiling point of the solvent is too low, the drying speed is too high and the film quality may be deteriorated. Further, if the boiling point of the solvent is too high, it is necessary to increase the temperature of the drying process, which may adversely affect other layers and the substrate.

  Specific examples include aromatic compounds such as toluene, xylene, methicylene, cyclohexylbenzene; halogen-containing solvents such as 1,2-dichloroethane, chlorobenzene, o-dichlorobenzene; ethylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol-1 -Aliphatic ethers such as monomethyl ether acetate (PGMEA), 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, anisole, phenetole, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2,3 Ether solvents such as aromatic ethers such as dimethylanisole and 2,4-dimethylanisole; aliphatic esters such as ethyl acetate, n-butyl acetate, ethyl lactate and n-butyl lactate; phenyl acetate, propion Phenyl, methyl benzoate, ethyl benzoate, isopropyl benzoate, propyl benzoate, organic solvent an ester solvents such as benzoic acid n- butyl. These may be used alone or in combination of two or more.

The first composition for forming an organic layer may contain other components as long as the effects of the present invention are not impaired. Examples of other components include various electron-accepting compounds, light emitting materials, binder resins, leveling agents, coating properties improving agents such as antifoaming agents, and the like. In addition, only 1 type may be used for another component, and 2 or more types may be used together in the combination and ratio of simmering.
When the organic layer is a single layer between the anode and the light emitting layer, that is, only the first organic layer, the first organic layer-forming composition preferably contains an electron-accepting compound. .

As the electron-accepting compound, a compound having an oxidizing power and an ability to accept one electron from the above-described hole-transporting compound is preferable. Specifically, a compound with an electron affinity of 4 eV or more is preferable, and a compound with a compound of 5 eV or more is more preferable.
Examples of the electron-accepting compound include onium salts substituted with an organic group such as 4-isopropyl-4′-methyldiphenyliodonium tetrakis (pentafluorophenyl) borate, iron (III) chloride (Japanese Patent Laid-Open No. 11-251067). Publication), high valence inorganic compounds such as ammonium peroxodisulfate, cyano compounds such as tetracyanoethylene, aromatic boron compounds such as tris (pentafluorophenyl) borane (Japanese Patent Laid-Open No. 2003-31365), fullerene derivatives, iodine Etc.

Of the above-mentioned compounds, an onium salt substituted with an organic group, a high-valence inorganic compound, and the like are preferable because they have strong oxidizing power. In addition, an onium salt substituted with an organic group, a cyano compound, an aromatic boron compound, or the like is preferable because it is highly soluble in various solvents and can be applied to form a film by a wet film formation method.
Specific examples of onium salts substituted with organic groups, cyano compounds, and aromatic boron compounds suitable as electron-accepting compounds include those described in WO 2005/089024, and preferred examples thereof are also the same. is there. Examples thereof include compounds represented by the following structural formulas, but are not limited thereto.

In addition, an electron-accepting compound may be used individually by 1 type, and may use 2 or more types by arbitrary combinations and a ratio.
The content of the electron-accepting compound in the first organic layer forming composition is usually 0.01% by weight or more, preferably 0.05% by weight or more, usually 20% by weight or less, preferably 10% by weight or less. is there. The first charge transport layer forming composition may contain two or more types of electron accepting compounds, and in that case, the total of the two or more types is preferably within the above range.

  Moreover, when a leveling agent is included, examples of the leveling agent include a silicon-based surfactant and a fluorine-based surfactant. Any one of the leveling agents may be used alone, or two or more thereof may be used in any combination and ratio. The content of the leveling agent in the first charge transport layer forming composition is usually 0.0001% by weight or more, preferably 0.001% by weight or more, and usually 1% by weight or less, preferably 0.1% by weight. % Or less. If the content of the leveling agent is too low, the leveling may be poor. If it is too high, the charge transport ability of the film may be reduced.

  Moreover, when an antifoamer is included, examples of the antifoamer include silicon oil, fatty acid ester, and phosphate ester. Any one type of antifoaming agent may be used alone, or two or more types may be used in any combination and ratio. The content of the antifoaming agent in the first charge transport layer forming composition is usually 0.0001% by weight or more, preferably 0.001% by weight or more, and usually 1% by weight or less, preferably 0.1%. It is in the range of weight percent or less. If the content of the antifoaming agent is too low, the defoaming effect may not be sufficient, and if it is too high, the charge transporting ability of the film may be reduced.

(1-3. Film formation method)
[Film formation method]
The first organic layer forming composition is formed on a substrate or another layer by a wet film forming method.
In the present invention, the wet film formation method includes, for example, spin coating method, dip coating method, die coating method, bar coating method, blade coating method, roll coating method, spray coating method, capillary coating method, ink jet method, screen printing method, A wet film formation method such as a gravure printing method or a flexographic printing method. Among these film forming methods, a spin coating method, a spray coating method, and an ink jet method are preferable. This is because the liquid property unique to the composition for wet film formation used in the organic electroluminescence device is met.

When using the wet film-forming method, the insolubilizing compound and other components used as necessary (additives that promote the crosslinking reaction, wet film-forming property improving agent, etc.) are dissolved in an appropriate solvent, and the above-mentioned first A composition for forming an organic layer is prepared. This composition is formed on a substrate or another layer by the above-described film forming method.
The film after film formation may be subjected to heat drying or reduced pressure drying.
When the hole transporting compound is a compound having an insolubilizing group, as described above, the film is obtained by insolubilizing the insolubilizing compound by heating and / or irradiation with active energy rays after film formation.

When the insolubilization method is heating, the heating method is not particularly limited, but the heating condition is that a film formed at 120 ° C. or higher, preferably 400 ° C. or lower is heated. The heating time is usually 1 minute or longer, preferably 24 hours or shorter.
The heating means is not particularly limited, and means such as placing a substrate or a laminate having the formed film on a hot plate or heating in an oven is used. For example, conditions such as heating on a hot plate at 120 ° C. or more for 1 minute or more can be used.

  When the insolubilization method is based on irradiation with active energy rays, direct irradiation using an ultraviolet, visible or infrared light source such as an ultra high pressure mercury lamp, high pressure mercury lamp, halogen lamp or infrared lamp, or the aforementioned light source Examples include a mask aligner incorporated and a method of irradiation using a conveyor type light irradiation device. Further, for example, there is a method of irradiating using a so-called microwave oven that irradiates a microwave generated by a magnetron. As the irradiation time, it is preferable to set conditions necessary for reducing the solubility of the film, but irradiation is usually performed for 0.1 seconds or longer, preferably 10 hours or shorter.

You may perform a heating and / or irradiation of an active energy ray individually or in combination, respectively. When combined, the order of implementation is not particularly limited.
In order to reduce the amount of moisture contained in the layer and / or the amount of moisture adsorbed on the surface of the layer after the heating and / or irradiation with active energy rays, it is performed in an atmosphere not containing moisture such as a nitrogen gas atmosphere. preferable. When performing heating and / or irradiation with active energy rays for the same purpose, it is particularly preferable to perform at least the process immediately before the formation of the upper layer in an atmosphere containing no moisture such as a nitrogen gas atmosphere.
The thickness of the first organic layer thus formed in the present invention is usually 3 nm or more, preferably 5 nm or more, more preferably 10 nm or more, and usually 100 nm or less, preferably 80 nm or less, more preferably 50 nm or less. It is.

[2. Light emitting layer]
In the present invention, an organic layer provided on the first organic layer, and between the electrodes (anode and cathode) to which an electric field is applied, holes injected from the anode and electrons injected from the cathode It is a layer which is excited by recombination with and becomes a main light emitting source.

The hole mobility μ (h1) of the light emitting layer in the present invention is described in [5. When measured by the method described in the section “Charge Mobility”, it is usually 1.0 × 10 ⁻⁶ cm ² / V · s or more, preferably 5.0 × 10 ⁻⁶ cm ² / V · s or more, and usually It is 1.0 * 10 ^<-2 > cm ^{< 2} > / V * s or less.

The electron mobility μ (e1) is described in [5. When measured by the method described in the section “Charge Mobility”, it is usually 1.0 × 10 ⁻⁶ cm ² / V · s or more, preferably 5.0 × 10 ⁻⁶ cm ² / V · s or more, and usually It is 1.0 * 10 ^<-2 > cm ^{< 2} > / V * s or less. The mobility of the light emitting layer in the present invention is the mobility of the light emitting material when the material constituting the light emitting layer is only the light emitting material. The light emitting layer is composed of the light emitting material as a dopant material and the charge transport material as a host material. In such a case, the mobility of the light emitting layer is defined by the mobility of the host material. In this case, when the host material is composed of two or more kinds of compounds, it is defined as the mobility of the mixed film.

The value of the formula (1), that is, μ (h1) / μ (e1) is usually 5 or more, preferably 8 or more, more preferably 10 or more, and usually 1000 or less, preferably 500 or less.
Within this range, the region where charge recombination occurs in the light emitting layer can be separated from the interface with the first organic layer. When both the first organic layer and the light emitting layer are formed by a wet process, it is possible to avoid deactivation of the excited state in the light emitting layer due to mixing of materials at the coating / coating interface. When a film is formed with a polymer having an insolubilizing group, it is possible to avoid deterioration of the device due to a reaction between an unreacted insolubilizing group and electrons or an excited state, and it is possible to manufacture a device with high efficiency and long life. It is.

  The light emitting layer contains at least a material having a light emitting property (light emitting material) as a constituent material, and preferably a compound having a hole transporting property (hole transporting material) or an electron transporting property. The compound (electron transport material) which has this. A light emitting material may be used as a dopant material, and a hole transport material, an electron transport material, or the like may be used as a host material. There is no particular limitation on the light-emitting material, and a material that emits light at a desired light emission wavelength and has favorable light emission efficiency may be used. Furthermore, the light emitting layer 5 may contain other components as long as the effects of the present invention are not significantly impaired. In addition, when forming a light emitting layer with a wet film-forming method, it is preferable to use a low molecular weight material in any case.

(2-1. Compound)
There is no restriction | limiting in particular as long as the effect of this invention is not impaired as a material used for a light emitting layer, A well-known material is applicable. For example, a fluorescent material or a phosphorescent material may be used, but a phosphorescent material is preferable from the viewpoint of internal quantum efficiency.
For the purpose of improving the solubility in a solvent, it is preferable to reduce the symmetry and rigidity of the molecules of the luminescent material or introduce a lipophilic substituent such as an alkyl group.

Hereinafter, examples of the fluorescent light emitting material among the light emitting materials will be described, but the fluorescent light emitting material is not limited to the following examples.
Examples of the fluorescent light-emitting material that gives blue light emission (blue fluorescent light-emitting material) include naphthalene, perylene, pyrene, anthracene, coumarin, chrysene, p-bis (2-phenylethenyl) benzene, and derivatives thereof.

Examples of the fluorescent light emitting material that gives green light emission (green fluorescent light emitting material) include quinacridone derivatives, coumarin derivatives, aluminum complexes such as Al (C ₉ H ₆ NO) _3, and the like.
Examples of the fluorescent light-emitting material that gives yellow light (yellow fluorescent light-emitting material) include rubrene and perimidone derivatives.

  Examples of fluorescent light-emitting materials (red fluorescent light-emitting materials) that emit red light include, for example, DCM (4- (dicyanomethylene) -2-methyl-6- (p-dimethylaminostyryl) -4H-pyran) -based compounds, benzopyran derivatives, rhodamine derivatives. Benzothioxanthene derivatives, azabenzothioxanthene and the like.

As the phosphorescent material, for example, a long-period type periodic table (hereinafter referred to as a long-period type periodic table when referred to as “periodic table” unless otherwise specified) is selected from the seventh to eleventh groups. And an organometallic complex containing a metal.
Preferred examples of the metal selected from Groups 7 to 11 of the periodic table include ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum, and gold.

  As the ligand of the complex, a ligand in which a (hetero) aryl group such as a (hetero) arylpyridine ligand or a (hetero) arylpyrazole ligand and a pyridine, pyrazole, phenanthroline, or the like is connected is preferable. A pyridine ligand and a phenylpyrazole ligand are preferable. Here, (hetero) aryl represents an aryl group or a heteroaryl group.

  Specific examples of the phosphorescent material include tris (2-phenylpyridine) iridium, tris (2-phenylpyridine) ruthenium, tris (2-phenylpyridine) palladium, bis (2-phenylpyridine) platinum, tris (2- Phenylpyridine) osmium, tris (2-phenylpyridine) rhenium, octaethyl platinum porphyrin, octaphenyl platinum porphyrin, octaethyl palladium porphyrin, octaphenyl palladium porphyrin, and the like.

  The molecular weight of the compound used as the light emitting material is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 10,000 or less, preferably 5000 or less, more preferably 4000 or less, still more preferably 3000 or less, and usually 100 or more, Preferably it is 200 or more, More preferably, it is 300 or more, More preferably, it is the range of 400 or more. If the molecular weight of the luminescent material is too small, the heat resistance will be significantly reduced, gas generation will be caused, the film quality will be reduced when the film is formed, or the morphology of the organic electroluminescent element will be changed due to migration, etc. Sometimes come. On the other hand, if the molecular weight of the luminescent material is too large, it tends to be difficult to purify the luminescent material, or it may take time to dissolve in the solvent.

In addition, any 1 type may be used for the luminescent material mentioned above, and 2 or more types may be used together by arbitrary combinations and a ratio.
Specific examples of the light emitting material are shown below, but the present invention is not limited to these. Me is a methyl group and Hex is a hexyl group.
<Examples of luminescent materials>

[Charge transport material]
The organic electroluminescent element of the present invention may further contain a charge transport material as a material constituting the light emitting layer.
In the present invention, only one type of charge transport material may be used, or two or more types may be used in any combination and ratio.

In the light emitting layer, it is preferable to use a light emitting material as a dopant material and a charge transport material as a host material.
The charge transport material may be a compound that has been conventionally used in a light emitting layer of an organic electroluminescent device, and particularly a compound that is used as a host material of the light emitting layer.
Specific examples of charge transport materials include aromatic amine compounds, phthalocyanine compounds, porphyrin compounds, oligothiophene compounds, polythiophene compounds, benzylphenyl compounds, compounds in which tertiary amines are linked by a fluorene group, hydrazone compounds Compounds, silazane compounds, silanamine compounds, phosphamine compounds, quinacridone compounds, anthracene compounds, pyrene compounds, carbazole compounds, pyridine compounds, phenanthroline compounds, oxadiazole compounds, silole compounds, etc. It is done.

For example, two or more condensed aromatic rings including two or more tertiary amines represented by 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl are substituted with nitrogen atoms. Aromatic amine compounds having a starburst structure (J. Lumin, etc.) such as aromatic diamines (Japanese Patent Laid-Open No. 5-234681), 4,4 ′, 4 ″ -tris (1-naphthylphenylamino) triphenylamine, etc. , 72-74, 985, 1997), an aromatic amine compound comprising a tetramer of triphenylamine (Chem. Commun., 2175, 1996), 2, 2 ′, 7, 7 ′. -Fluorene compounds such as tetrakis- (diphenylamino) -9,9'-spirobifluorene (Synth. Metals, 91, 209, 1997), 4,4'-N, N'- Carbazole compounds such as carbazole biphenyl, 2- (4-biphenylyl) -5- (p-tertiarybutylphenyl) -1,3,4-oxadiazole (tBu-PBD), 2,5-bis (1- Naphthyl) -1,3,4
Oxadiazole compounds such as oxadiazole (BND), 2,5-bis (6 ′-(2 ′, 2 ″ -bipyridyl))-1,1-dimethyl-3,4-diphenylsilole (PyPySPyPy), etc. And phenanthroline compounds such as bathophenanthroline (BPhen) and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP, bathocuproin).

Specific examples of the charge transporting material are shown below, but the present invention is not limited thereto.
<Example of charge transport material>

  In order for the mobility of the light emitting layer to satisfy the formula (1), a compound satisfying the formula (1) may be used alone, and the formula (1) can be obtained by mixing a plurality of charge transporting materials in an arbitrary ratio. May be satisfied. It is possible to select a material that is highly stable with respect to each charge of hole and electron, and the hole transport material and the electron are less dependent on the material in setting the mobility ratio within the range of the present invention. It is preferable to satisfy the formula (1) by mixing transport materials. Although depending on the hole mobility of the hole transport material and the value of the electron mobility of the electron transport material, the hole transport material is usually 50% to 99.% by weight with respect to the total amount of the charge transport material. Formula (1) can be satisfy | filled by mixing in 9% of range. More preferably, it is in the range of 60% to 99.9%.

(2-2. Composition)
When the light emitting layer is formed by a wet film forming method, the light emitting material and the charge transporting material constituting the light emitting layer, and other components as necessary are mixed with an appropriate solvent to form a film forming composition (light emitting layer). A forming composition) is prepared and used.
(solvent)
Further, the solvent is not particularly limited as long as the light emitting material and the charge transporting material are well dissolved.

The solubility of the solvent is usually 0.01% by weight or more, preferably 0.05% by weight or more, more preferably 0.1% by weight or more, respectively, at normal temperature and normal pressure. It is preferable to do.
Although the specific example of a solvent is given to the following, as long as the effect of this invention is not impaired, it is not limited to these.

  For example, alkanes such as n-decane, cyclohexane, ethylcyclohexane, decalin, and bicyclohexane; aromatic hydrocarbons such as toluene, xylene, methicylene, cyclohexylbenzene, and tetralin; halogenated fragrances such as chlorobenzene, dichlorobenzene, and trichlorobenzene Group hydrocarbons: 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, anisole, phenetole, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2,3-dimethylanisole, 2,4-dimethyl Aromatic ethers such as anisole and diphenyl ether; aromatic esters such as phenyl acetate, phenyl propionate, methyl benzoate, ethyl benzoate, ethyl benzoate, propyl benzoate, and n-butyl benzoate; Alicyclic ketones such as Sanone, Cyclooctanone and Fencon; Alicyclic alcohols such as cyclohexanol and cyclooctanol; Aliphatic ketones such as methyl ethyl ketone and dibutyl ketone; Aliphatic alcohols such as butanol and hexanol; Ethylene And aliphatic ethers such as glycol dimethyl ether, ethylene glycol diethyl ether, and propylene glycol-1-monomethyl ether acetate (PGMEA).

Of these, alkanes and aromatic hydrocarbons are preferable. One of these solvents may be used alone, or two or more thereof may be used in any combination and ratio.
In order to obtain a more uniform film, it is preferable that the solvent evaporates from the liquid film immediately after the film formation at an appropriate rate. For this reason, the boiling point of the solvent is usually 80 ° C. or higher, preferably 100 ° C. or higher, more preferably 120 ° C. or higher, and usually 270 ° C. or lower, preferably 250 ° C. or lower, more preferably 230 ° C. or lower.

  The amount of the solvent used is arbitrary as long as the effects of the present invention are not significantly impaired, but is preferably 10 parts by weight or more, more preferably 50 parts by weight or more, particularly preferably 100 parts by weight of the composition for forming a light emitting layer. Is 80 parts by weight or more, preferably 99.95 parts by weight or less, more preferably 99.9 parts by weight or less, and particularly preferably 99.8 parts by weight or less. When the content is lower than the lower limit, the viscosity becomes too high, and the film forming workability may be lowered. On the other hand, when the value exceeds the upper limit, the film thickness obtained by removing the solvent after film formation cannot be obtained, so that film formation tends to be difficult. In addition, when mixing and using 2 or more types of solvents as a composition for light emitting layer formation, it is made for the sum total of these solvents to satisfy | fill this range.

Moreover, the composition for light emitting layer formation in this invention may contain various additives, such as a leveling agent and an antifoamer, for the purpose of improving film forming property.
(2-3. Film formation method)
The method for forming a light emitting layer in the present invention is preferably performed by a wet film forming method from the viewpoint of excellent film forming properties.

After the application of the composition for forming a light emitting layer for producing the light emitting layer, the obtained coating film is dried and the solvent for the light emitting layer is removed to form the light emitting layer. The method of the wet film formation method is not limited as long as the effect of the present invention is not significantly impaired. For example, the wet film formation method in the present invention described in the above [Film formation method] can be mentioned. Coating method and inkjet method.

The solid content concentration of the light emitting material, hole transporting compound, electron transporting compound and the like in the composition for forming a light emitting layer is usually 0.01% by weight or more and usually 70% by weight or less. If this concentration is too large, film thickness unevenness may occur, and if it is too small, defects may occur in the film.
The thickness of the light emitting layer is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 3 nm or more, preferably 5 nm or more, and usually 200 nm or less, preferably 100 nm or less. If the light emitting layer is too thin, defects may occur in the film, and if it is too thick, the driving voltage may increase.

[3. Second organic layer]
The second organic layer is provided for the purpose of further improving the light emission efficiency of the device, and can efficiently transport electrons injected from the cathode between the electrodes to which an electric field is applied in the direction of the light emitting layer. Formed from a compound that can be formed. The second organic layer is included between the light emitting layer and the cathode. When there is no third organic layer described later, it is provided adjacent to the light emitting layer. Further, when there is a third organic layer, it is provided adjacent to the cathode side of the third organic layer.

The electron mobility μ (e2) of the second organic layer in the present invention is described in [5. When measured by the method described in the section “Charge Mobility”, it is usually 1.0 × 10 ⁻⁴ cm ² / V · s or more, preferably 1.2 × 10 ⁻⁴ cm ² / V · s or more, and usually It is 1.5 * 10 < ^-4 > cm < ² > / V * s or less.
Within this range, the electron injecting property to the light emitting layer is improved, and the organic electroluminescent element can be driven with a low driving voltage.

  The electron transporting compound used in the second organic layer usually has high electron injection efficiency from the cathode or the electron injection layer 8 and efficiently transports injected electrons with high electron mobility. The compound which can be used is used. Examples of the compound 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 , Distyrylbiphenyl derivatives, silole derivatives, 3-hydroxyflavone metal complexes, 5-hydroxyflavone metal complexes, benzoxazole metal complexes, benzothiazole metal complexes, trisbenzimidazolylbenzene (US Pat. No. 5,645,948), quinoxaline compounds ( JP-A-6-207169), phenanthroline derivative (JP-A-5-331459), 2-t-butyl-9,10-N, N'-dicyanoanthraquinonediimine, n-type hydrogenated amorphous silicon carbide , N-type zinc sulfide, n-type zinc Such as emissions of zinc, and the like.

In addition, only 1 type may be used for the material of a 2nd organic layer, and 2 or more types may be used together by arbitrary combinations and a ratio.
There is no restriction | limiting in the formation method of a 2nd organic layer. Therefore, it can be formed by a wet film forming method, a vapor deposition method, or other methods.
The film thickness of the second organic layer is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 1 nm or more, preferably 5 nm or more, and usually 300 nm or less, preferably 100 nm or less.

[4. Third organic layer]
It is a layer having a role of preventing holes moving from the anode 2 from reaching the cathode and a role of efficiently transporting electrons injected from the cathode toward the light emitting layer. The third organic layer is included between the light emitting layer and the second organic layer.
The electron mobility μ (e3) of the third organic layer in the present invention is described in [5. When measured by the method described in the section “Charge Mobility”, it is usually 1.0 × 10 ⁻⁴ cm ² / V · s or more, preferably 1.2 × 10 ⁻⁴ cm ² / V · s or more, and usually It is 1.5 * 10 < ^-4 > cm < ² > / V * s or less.

Within this range, the electron injecting property to the light emitting layer is improved, and the organic electroluminescent element can be driven with a low driving voltage.
The physical properties required for the material constituting the third organic layer include high electron mobility and 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 third organic layer satisfying such conditions include bis (2-methyl-8-quinolinolato) (phenolato) aluminum and bis (2-methyl-8-quinolinolato) (triphenylsilanolato) aluminum. Mixed ligand complexes such as, metal complexes such as bis (2-methyl-8-quinolato) aluminum-μ-oxo-bis- (2-methyl-8-quinolato) aluminum binuclear metal complexes, distyrylbiphenyl derivatives, etc. Of styryl compounds (JP-A-11-242996), triazole derivatives such as 3- (4-biphenylyl) -4-phenyl-5 (4-tert-butylphenyl) -1,2,4-triazole 7-41759), phenanthroline derivatives such as bathocuproine (JP-A-10-79297), and the like. It is. Furthermore, a compound having at least one pyridine ring substituted at the 2,4,6-positions described in International Publication No. 2005-022962 is also preferable as the material of the third organic layer.

In addition, the material of a 3rd organic layer may use only 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.
There is no restriction | limiting in the formation method of a 3rd organic layer. Therefore, it can be formed by a wet film forming method, a vapor deposition method, or other methods.
The thickness of the third organic layer is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.3 nm or more, preferably 0.5 nm or more, and usually 100 nm or less, preferably 50 nm or less.

[5. Charge mobility]
(5-1. Method for measuring charge mobility)
The hole mobility and the electron mobility can be measured by a known method, but can be measured by, for example, the TOF method (Time of flight). The charge mobility in the present invention was measured by the TOF method.
Hereinafter, the measuring method by the TOF method is shown.

(5-2. Preparation of charge mobility measurement sample)
An example of producing a charge mobility measurement sample (hereinafter referred to as “measurement sample”) will be described below. A measurement sample is obtained by forming a layer made of a compound whose mobility is to be measured (hereinafter referred to as “compound film”) on an electrode formed on a substrate and forming a counter electrode on the compound film. Can be made. At this time, one of the electrodes needs to be an electrode that transmits light. The method for forming the compound film is not particularly limited. The thickness of the compound film is not particularly limited, but it is preferable to form the film with a thickness of submicron to micron order in order to increase the measurement accuracy.

(5-3. Measurement of charge mobility)
The charge mobility is measured using the measurement sample produced as described above. At 25 ° C., pulsed light is irradiated from the transparent electrode side of the measurement sample with a voltage applied to the measurement sample. The charge generated on the transparent electrode side surface of the compound film moves to the counter electrode by the voltage applied to the measurement sample. When the charge reaches the counter electrode, no current flows. The current flowing through the measurement sample can be measured by measuring the time required for the charge to move through the compound film by performing current-voltage conversion using a shunt resistor and observing the voltage waveform using an oscilloscope. . If the measurement sensitivity is poor, a voltage amplification device can be used.

When the time required for this charge to move in the compound film is T (sec), the voltage applied to the compound film is V (V), and the film thickness of the compound film is d (cm), unit electric field strength, unit The mobility is μ = d / [T × (V / d)] (cm ² / V · s) as the charge movement speed per ^second.
Can be calculated.

By this method, charge mobility is calculated at several voltages, and the Pool-Frenkel equation μ (E) = μ (0) × exp (β × √E)
E = V / d
μ (0) = zero-field mobility
β: Poole-Frenkel factor
The charge mobility at an arbitrary electric field strength can be calculated by fitting the measured data using.

  In the present invention, Brio (lamp excitation Nd: YAG pulse laser, manufactured by Quantel) was used as the pulse light source, and a TDS2022 type oscilloscope (manufactured by Tektronix) was used as the oscilloscope. When a voltage amplifying device was required, the charge mobility of the measurement sample was measured using a DA1855A differential amplifier (manufactured by LeCroy).

By reversing the polarity of the voltage applied to the measurement sample, the polarity of the charge moving from the transparent electrode surface to the counter electrode is reversed, so that the hole mobility and the electron mobility can be measured by the same method.
The charge mobility described in the present invention refers to a value when the value of the square root of the electric field strength is 500 (V / cm) ^0.5 .

[6. the reason]
The reason why the effects of the present invention can be obtained by using the configuration of the present invention is estimated as follows.
With the structure of the present invention, the light emitting region of the light emitting layer in the organic electroluminescent element can be separated from the interface adjacent to the layer formed by the wet film forming method.
When the light-emitting region of the light-emitting layer is at the interface where the layers formed by the wet film formation method are adjacent to each other, a reaction between electrons and unreacted crosslinkable groups occurs, or excitons are quenched, resulting in an element obtained May have a low light emission efficiency and a short driving life.
On the other hand, in the organic electroluminescent element of the present invention, the above phenomenon does not occur, and an element having a low driving voltage, high luminous efficiency and a long driving life can be obtained.

[7. Excitation energy]
When the organic electroluminescent device of the present invention has the third organic layer between the light emitting layer and the second organic layer, the excitation in the third organic layer is performed by the measurement method described in detail below. The energy is preferably larger than the term excitation energy in the light emitting layer.

Specifically, the excitation energy in the third organic layer is usually 0.01 eV or more, preferably 0.05 eV or more, and usually 5.0 eV or less, preferably 3.0 eV or less than the excitation energy in the light emitting layer. . When the light emitting layer is composed of a plurality of compounds, the compound having the lowest excitation energy in the light emitting layer may satisfy the above relationship.
Within the above range, even if the recombination region of the light emitting layer is near the interface with the third organic layer, the excited state generated in the light emitting layer is prevented from diffusing into the third organic layer. Therefore, an element with high efficiency and long life can be produced.

The excitation energy in the present invention means singlet excitation energy and triplet energy.
The singlet excitation energy in the present invention is determined from the shortest maximum wavelength in the fluorescence emission spectrum of the compound. The triplet excitation energy is determined from the shortest maximum wavelength in the phosphorescence emission spectrum of the compound.

(7-1. Measurement method)
The excitation energy can be measured by a known measurement method. For example, the excitation energy can be measured using a streak scope C4334 (manufactured by Hamamatsu Photonics).
First, a compound to be measured is dissolved in a solvent to prepare a 0.1 mmol / l to 0.1 mol / l solution.

The solution is cooled to liquid nitrogen temperature (−196 ° C.), irradiated with a 337 nm nitrogen laser to excite the compound, and light emission from the compound is measured with respect to time and wavelength with a streak scope.
The fluorescence and phosphorescence emission components are separated according to the time and wavelength of light emission from the compound, and singlet and triplet excitation energies can be calculated from the shortest maximum wavelengths.

<Organic electroluminescent device>
Below, the layer structure of the organic electroluminescent element manufactured with the method of this invention, its general formation method, etc. are demonstrated with reference to FIG.
FIG. 1 is a schematic cross-sectional view showing a structural example of an organic electroluminescent device according to the present invention. In FIG. 1, 1 is a substrate, 2 is an anode, 3 is a hole injection layer, 4 is a hole transport layer, 5 Represents a light-emitting layer, 6 represents a hole blocking layer, 7 represents an electron transport layer, 8 represents an electron injection layer, and 9 represents a cathode.

  In the case of the element shown in FIG. 1, the hole transport layer corresponds to the first organic layer, the electron transport layer corresponds to the second organic layer, and the hole blocking layer corresponds to the third organic layer. Each layer described below is formed by selecting a material that satisfies the above-described conditions as the conditions of the first organic layer, the light emitting layer, the second organic layer, and the third organic layer to which they correspond.

(substrate)
The substrate serves as a support for the organic electroluminescence device, and quartz or glass plates, metal plates or metal foils, plastic films, sheets, or the like are 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 element 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.

(anode)
The anode 2 serves to inject holes into the layer on the light emitting layer side.
This anode 2 is usually made of a metal such as aluminum, gold, silver, nickel, palladium, platinum, a metal oxide such as an oxide of indium and / or tin, a metal halide such as copper iodide,
It is composed of carbon black or 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 the anode 2 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 It is also possible to form the anode 2 by dispersing it and applying it onto the substrate. Further, in the case of a conductive polymer, a thin film can be directly formed on the substrate by electrolytic polymerization, or the anode 2 can be formed by applying a conductive polymer on the substrate (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. 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 surface of the anode 2 is treated with ultraviolet (UV) / ozone, or with oxygen plasma or argon plasma. It is preferable to do.
(Hole injection layer)
The hole injection layer is a layer that transports holes from the anode 2 to the light emitting layer, and is usually formed on the anode 2.

The method for forming the hole injection layer according to the present invention may be a vacuum vapor deposition method or a wet film formation method, and is not particularly limited. However, from the viewpoint of reducing dark spots, the hole injection layer may be formed by a wet film formation method. preferable.
The thickness of the hole injection layer is usually 5 nm or more, preferably 10 nm or more, and usually 1000 nm or less, preferably 500 nm or less.

<Formation of hole injection layer by wet film formation method>
When the hole injection layer is formed by wet film formation, the material for forming the hole injection layer is usually mixed with an appropriate solvent (hole injection layer solvent) to form a composition for film formation (hole injection). Layer forming composition), and applying this hole injection layer forming composition onto a layer corresponding to the lower layer of the hole injection layer (usually an anode) by an appropriate technique, A hole injection layer is formed by drying.

(Hole transporting compound)
The composition for forming a hole injection layer usually contains a hole transporting compound and a solvent as constituent materials of the hole injection layer.
The hole transporting compound is a compound having a hole transporting property that is usually used in a hole injection layer of an organic electroluminescence device, and may be a polymer compound or the like, a monomer or the like. Although it may be a low molecular weight compound, it is preferably a high molecular weight compound.

The hole transporting compound is preferably a compound having an ionization potential of 4.5 eV to 6.0 eV from the viewpoint of a charge injection barrier from the anode 2 to the hole injection layer. Examples of hole transporting compounds include aromatic amine derivatives, phthalocyanine derivatives, porphyrin derivatives, oligothiophene derivatives, polythiophene derivatives, benzylphenyl derivatives, compounds in which tertiary amines are linked by a fluorene group, hydrazone derivatives, silazane derivatives, silanamines Derivatives, phosphamine derivatives, quinacridone derivatives, polyaniline derivatives, polypyrrole derivatives, polyphenylene vinylene derivatives, polythienylene vinylene derivatives, polyquinoline derivatives, polyquinoxaline derivatives, carbon and the like.

In the present invention, the derivative includes, for example, an aromatic amine derivative, and includes an aromatic amine itself and a compound having an aromatic amine as a main skeleton. It may be a mer.
The hole transporting compound used as the material for the hole injection layer may contain any one of these compounds alone, or may contain two or more. When two or more hole transporting compounds are contained, the combination thereof is arbitrary, but one or more aromatic tertiary amine polymer compounds and one or two other hole transporting compounds are used. It is preferable to use the above in combination.

Among the above examples, an aromatic amine compound is preferable from the viewpoint of amorphousness and visible light transmittance, and 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 type of the aromatic tertiary amine compound is not particularly limited, but from the viewpoint of uniform light emission due to the surface smoothing effect, a polymer compound having a weight average molecular weight of 1,000 or more and 1,000,000 or less (a polymerizable compound in which repeating units are linked) is further included. preferable. Preferable examples of the aromatic tertiary amine polymer compound include a polymer compound having a repeating unit represented by the following formula (I).

(In Formula (I), Ar ¹ and Ar ² each independently represent an aromatic hydrocarbon group which may have a substituent or an aromatic heterocyclic group which may have a substituent. Ar ^{3 to} Ar ⁵ each independently represents an aromatic hydrocarbon group which may have a substituent or an aromatic heterocyclic group which may have a substituent. Represents a linking group selected from the group of linking groups, and among Ar ^{1 to} Ar ⁵ , two groups bonded to the same N atom may be bonded to each other to form a ring.

(In the above formulas, Ar ^{6 to} Ar ¹⁶ each independently represents an aromatic hydrocarbon group which may have a substituent or an aromatic heterocyclic group which may have a substituent. R ¹ and R ² each independently represents a hydrogen atom or an arbitrary substituent.))
As the aromatic hydrocarbon group and the aromatic heterocyclic group of Ar ^{1 to} Ar ¹⁶ , a benzene ring, a naphthalene ring, a phenanthrene ring, a thiophene from the viewpoint of the solubility, heat resistance, hole injection / transport property of the polymer compound A group derived from a ring or a pyridine ring is preferred, and a group derived from a benzene ring or a naphthalene ring is more preferred.

The aromatic hydrocarbon group and aromatic heterocyclic group of Ar ^{1 to} Ar ¹⁶ may further have a substituent. The molecular weight of the substituent is usually 400 or less, preferably about 250 or less. As the substituent, an alkyl group, an alkenyl group, an alkoxy group, an aromatic hydrocarbon group, an aromatic heterocyclic group and the like are preferable.
When R ¹ and R ² are optional substituents, examples of the substituent include an alkyl group, an alkenyl group, an alkoxy group, a silyl group, a siloxy group, an aromatic hydrocarbon group, and an aromatic heterocyclic group. .

Specific examples of the aromatic tertiary amine polymer compound having a repeating unit represented by the formula (I) include those described in International Publication No. 2005/089024. In addition, as a hole transporting compound, a conductive polymer (PEDOT / PSS) obtained by polymerizing 3,4-ethylenedioxythiophene (3,4-ethylenedioxythiophene), a polythiophene derivative, in high molecular weight polystyrene sulfonic acid. Is also preferred. Moreover, the end of this polymer may be capped with methacrylate or the like.

  The concentration of the hole transporting compound in the composition for forming a hole injection layer is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.01% by weight or more, preferably in terms of film thickness uniformity. Is 0.1% by weight or more, more preferably 0.5% by weight or more, and usually 70% by weight or less, preferably 60% by weight or less, more preferably 50% by weight or less. If this concentration is too high, film thickness unevenness may occur, and if it is too low, defects may occur in the formed hole injection layer.

(Electron-accepting compound)
The composition for forming a hole injection layer preferably contains an electron accepting compound as a constituent material of the hole injection layer.
It is preferable that the composition for positive hole injection layers contains the 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 which is the compound of these is further more preferable. The electron-accepting compound is selected from the group consisting of, for example, triarylboron compounds, metal halides, Lewis acids, organic acids, onium salts, salts of arylamines and metal halides, and salts of arylamines and Lewis acids. 1 type, or 2 or more types of compounds etc. which are mentioned. More specifically, an onium salt substituted with an organic group such as 4-isopropyl-4′-methyldiphenyliodonium tetrakis (pentafluorophenyl) borate or triphenylsulfonium tetrafluoroborate (WO 2005/089024) Iron chloride (III) (Japanese Patent Laid-Open No. 11-251067)
No.), high-valent inorganic compounds such as ammonium peroxodisulfate; cyano compounds such as tetracyanoethylene; aromatic boron compounds such as tris (pendafluorophenyl) borane (JP-A-2003-31365); fullerene derivatives; Examples include iodine. These electron accepting compounds can improve the conductivity of the hole injection layer by oxidizing the hole transporting compound. The content of the electron-accepting compound with respect to the hole-transporting compound is usually 0.1 mol% or more, preferably 1 mol% or more. However, it is usually 100 mol% or less, preferably 40 mol% or less.

(Other components)
As a material for the hole injection layer, other components may be further contained in addition to the above-described hole transporting compound and electron accepting compound as long as the effects of the present invention are not significantly impaired. Examples of other components include various light emitting materials, electron transporting compounds, binder resins, and coating property improving agents. In addition, only 1 type may be used for another component and it may use 2 or more types together by arbitrary combinations and a ratio.

(solvent)
At least one of the solvents of the composition for forming a hole injection layer used in the wet film formation method is preferably a compound that can dissolve the constituent material of the hole injection layer. The boiling point of this solvent is usually 110 ° C. or higher, preferably 140 ° C. or higher, particularly 200 ° C. or higher, usually 400 ° C. or lower, and preferably 300 ° C. or lower. If the boiling point of the solvent is too low, the drying speed is too high and the film quality may be deteriorated. Further, if the boiling point of the solvent is too high, it is necessary to increase the temperature of the drying step, which may adversely affect other layers and the substrate.

Examples of the solvent include ether solvents, ester solvents, aromatic hydrocarbon solvents, amide solvents, and the like.
Examples of ether solvents include aliphatic ethers such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and propylene glycol-1-monomethyl ether acetate (PGMEA); 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, anisole , Phenetole, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2,3-dimethylanisole, aromatic ethers such as 2,4-dimethylanisole, and the like.

Examples of the ester solvent include aromatic esters such as phenyl acetate, phenyl propionate, methyl benzoate, ethyl benzoate, propyl benzoate, and n-butyl benzoate.
Examples of the aromatic hydrocarbon solvent include toluene, xylene, cyclohexylbenzene, 3-isopropylpropylphenyl, 1,2,3,4-tetramethylbenzene, 1,4-diisopropylbenzene, cyclohexylbenzene, and methylnaphthalene. Can be mentioned.
Examples of the amide solvent include N, N-dimethylformamide, N, N-dimethylacetamide, and the like.

In addition, dimethyl sulfoxide and the like can also be used.
These solvent may use only 1 type and may use 2 or more types by arbitrary combinations and a ratio.
(Film formation method)
After the composition for forming the hole injection layer is prepared, the composition is coated on the layer corresponding to the lower layer of the hole injection layer (usually the anode 2) by wet film formation, and dried to form the composition. A hole injection layer is formed.

The temperature in the film forming step is preferably 10 ° C. or higher, and preferably 50 ° C. or lower, in order to prevent film loss due to the formation of crystals in the composition.
Although the relative humidity in a film-forming process is not limited unless the effect of this invention is impaired remarkably, it is 0.01 ppm or more normally and 80% or less normally.
After the film formation, the film of the composition for forming a hole injection layer is usually dried by heating or the like. Examples of the heating means used in the heating step include a clean oven, a hot plate, infrared rays, a halogen heater, microwave irradiation and the like. Among them, a clean oven and a hot plate are preferable in order to uniformly apply heat to the entire film.

  The heating temperature in the heating step is preferably heated at a temperature equal to or higher than the boiling point of the solvent used in the composition for forming a hole injection layer as long as the effects of the present invention are not significantly impaired. In the case of a mixed solvent containing two or more types of solvents used in the hole injection layer, at least one type is preferably heated at a temperature equal to or higher than the boiling point of the solvent. In consideration of an increase in the boiling point of the solvent, the heating step is preferably performed at 120 ° C. or higher, preferably 410 ° C. or lower.

  In the heating step, the heating time is not limited as long as the heating temperature is not lower than the boiling point of the solvent of the composition for forming a hole injection layer and sufficient insolubilization of the coating film does not occur. Is less than a minute. If the heating time is too long, the components of the other layers tend to diffuse, and if it is too short, the hole injection layer tends to be inhomogeneous. Heating may be performed in two steps.

<Formation of hole injection layer by vacuum deposition>
When the hole injection layer is formed by vacuum deposition, one or more of the constituent materials of the hole injection layer (the aforementioned hole transporting compound, electron accepting compound, etc.) are placed in a vacuum vessel. Put in crucibles (in case of using two or more kinds of materials, put them in each crucible), evacuate the inside of the vacuum vessel to about 10 ⁻⁴ Pa with a suitable vacuum pump, and then heat the crucible (two or more kinds) When using materials, heat each crucible) and evaporate by controlling the amount of evaporation (when using two or more materials, evaporate by controlling the amount of evaporation independently) and place it facing the crucible. A hole injection layer is formed on the anode 2 of the substrate. In addition, when using 2 or more types of materials, those hole mixture layers can also be formed by putting them in a crucible and heating and evaporating them.

The degree of vacuum at the time of vapor deposition is not limited as long as the effect of the present invention is not significantly impaired, but is usually 0.1 × 10 ⁻⁶ Torr (0.13 × 10 ⁻⁴ Pa) or more, usually 9.0 × 10 ⁻⁶ Torr. (12.0 × 10 ⁻⁴ Pa) or less. The deposition rate is not limited as long as the effect of the present invention is not significantly impaired, but is usually 0.1 Å / second or more and usually 5.0 Å / second or less. The film forming temperature at the time of vapor deposition is not limited as long as the effect of the present invention is not significantly impaired, but is preferably 10 ° C. or higher, preferably 50 ° C. or lower.

[Hole transport layer]
The hole transport layer is provided on the hole injection layer. The hole transport layer can be formed by the material and the film forming method described in [First organic layer]. The same applies to preferred embodiments of the material and the film formation method.
{Light emitting layer}
The light emitting layer can be formed by the material and film forming method described in the above section [Light emitting layer]. The preferred materials and methods are similar.

{Electron transport layer}
The electron transport layer is provided on the light emitting layer. The electron transport layer can be formed by the material and the film forming method described in [Second organic layer]. The same applies to preferred embodiments of the material and the film formation method.
{Hole blocking layer}
It is preferable to have a hole blocking layer between the light emitting layer and the electron transport layer. The hole blocking layer can be formed by the material and the film forming method described in [Third organic layer]. The same applies to preferred embodiments of the material and the film formation method.

{Electron injection layer}
The electron injection layer 8 is provided on the electron transport layer and plays a role of efficiently injecting electrons injected from the cathode into the light emitting layer.
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. Examples include alkali metals such as sodium and cesium, alkaline earth metals such as barium and calcium, and the film thickness is preferably from 0.1 nm to 5 nm.

  Furthermore, an organic electron transport compound 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, or rubidium ( (As described in JP-A-10-270171, JP-A-2002-1000047, JP-A-2002-1000048, etc.), it is possible to improve the electron injection / transport properties and achieve excellent film quality. preferable. In this case, the film thickness is usually 5 nm or more, preferably 10 nm or more, and is usually 200 nm or less, preferably 100 nm or less.

In addition, the material of the electron injection layer 8 may use only 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.
There is no restriction | limiting in the formation method of the electron injection layer 8. FIG. Therefore, it can be formed by a wet film forming method, a vapor deposition method, or other methods.
{cathode}
The cathode plays a role of injecting electrons into a layer (such as the electron injection layer 8 or the light emitting layer) on the light emitting layer side.

  As the cathode material, the material used for the anode 2 can be used. However, a metal having a low work function is preferable for efficient electron injection. For example, 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.

In addition, only 1 type may be used for the material of a cathode, and 2 or more types may be used together by arbitrary combinations and a ratio.
The thickness of the cathode is usually the same as that of the anode 2.
Further, for the purpose of protecting the cathode made of a low work function metal, it is preferable to further stack a metal layer having a high work function and stable to the atmosphere because the stability of the device is increased. For this purpose, for example, metals such as aluminum, silver, copper, nickel, chromium, gold and platinum are used. In addition, these materials may be used only by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

{Other layers}
The organic electroluminescent element according to the present invention may have another configuration without departing from the gist thereof. For example, as long as the performance is not impaired, an arbitrary layer may be provided between the anode 2 and the cathode in addition to the layers described above, and an arbitrary layer may be omitted.
<Electron blocking layer>
Examples of the layer that may be included include an electron blocking layer.

  The electron blocking layer is provided between the hole injecting layer or the hole transporting layer and the light emitting layer, and prevents electrons moving from the light emitting layer from reaching the hole injecting layer. Increases the recombination probability of holes and electrons, and has the role of confining the generated excitons in the light-emitting layer and the role of efficiently transporting holes injected from the hole injection layer toward the light-emitting layer. . In particular, when a phosphorescent material or a blue light emitting material is used as the light emitting material, it is effective to provide an electron blocking layer.

  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). Furthermore, in the present invention, when the light emitting layer is formed as an organic layer according to the present invention by a wet film formation method, the electron blocking layer is also required to be compatible with the wet film formation. Examples of the material used for such an electron blocking layer include a copolymer of dioctylfluorene and triphenylamine typified by F8-TFB (International Publication No. 2004/084260).

In addition, the material of an electron blocking layer may use only 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.
There is no restriction | limiting in the formation method of an electron blocking layer. Therefore, it can be formed by a wet film forming method, a vapor deposition method, or other methods.
Further, at the interface between the cathode and the light emitting layer or the electron transport layer, for example, lithium fluoride (LiF), magnesium fluoride (MgF ₂ ), lithium oxide (Li ₂ O), cesium carbonate (II) (CsCO ₃ ), etc. are formed. It is also an effective method to improve the efficiency of the device by inserting a very thin insulating film (0.1 to 5 nm) (Applied Physics Letters, 1997, Vol. 70, pp. 152; No. 74586; IEEE
Transactions on Electron Devices, 1997, Vol. 44, pp. 1245; SID 04 Digest, pp. 154 etc.).

Moreover, in the layer structure demonstrated above, it is also possible to laminate | stack components other than a board | substrate in reverse order. For example, in the case of the layer configuration of FIG. 1, the other components on the substrate are cathode, electron injection layer 8, electron transport layer, hole blocking layer, light emitting layer, hole transport layer, hole injection layer, anode 2 You may provide in order.
Furthermore, it is also possible to constitute the organic electroluminescent element according to the present invention by laminating components other than the substrate between two substrates, at least one of which is transparent.

In addition, a structure in which a plurality of components (light emitting units) other than the substrate are stacked in a plurality of layers (a structure in which a plurality of light emitting units are stacked) may be employed. In that case, instead of the interface layer between the steps (between the light emitting units) (when the anode is ITO and the cathode is Al, these two layers), for example, a charge made of vanadium pentoxide (V ₂ O ₅ ) or the like. When a generation layer (Carrier Generation Layer: CGL) is provided, a barrier between steps is reduced, which is more preferable from the viewpoint of light emission efficiency and driving voltage.

Furthermore, the organic electroluminescent device according to the present invention may be configured as a single organic electroluminescent device, or may be applied to a configuration in which a plurality of organic electroluminescent devices are arranged in an array. You may apply to the structure by which the cathode is arrange | positioned at XY matrix form.
Each layer described above may contain components other than those described as materials unless the effects of the present invention are significantly impaired.

<Organic EL display, organic EL lighting, and organic EL signal device>
The organic electroluminescent element of the present invention is used in organic EL display devices, organic EL lighting devices, and organic EL signal devices. The organic electroluminescent device obtained by the present invention is described in, for example, “Organic EL Display” (Ohm, August 20, 2004, written by Shizushi Tokito, Chiba Adachi, and Hideyuki Murata). By the method, an organic EL display, an organic EL display device, and organic EL illumination can be formed.

EXAMPLES Next, although an Example demonstrates this invention further more concretely, this invention is not limited to description of a following example, unless the summary is exceeded.
[Measurement of charge mobility]
(Reference Example 1)
An indium tin oxide (ITO) transparent conductive film deposited to a thickness of 150 nm on a glass substrate (manufactured by Sanyo Vacuum Co., Ltd., sputtered film) using ordinary photolithography technology and hydrochloric acid etching The anode 2 was formed by patterning into a stripe having a width of 2 mm. The patterned ITO substrate is cleaned in the order of ultrasonic cleaning with an aqueous surfactant solution, water cleaning with ultrapure water, ultrasonic cleaning with ultrapure water, and water cleaning with ultrapure water, followed by drying with compressed air, and finally UV irradiation. Ozone cleaning was performed. This ITO functions as a transparent electrode.
Next, a coating solution containing the compound (H1) having the structure shown below and KF-96 manufactured by Shin-Etsu Silicone Co., Ltd. as a surface smoothing material is prepared, and a film is formed on the ITO pattern substrate by spin coating under the following conditions. A compound film having a thickness of 2 μm was formed.

<Coating liquid for compound film formation>
Solvent Toluene Coating solution concentration (H1) 5.0% by weight
KF-96 0.023 wt%
<Film formation conditions>
Spinner speed 500rpm
Spinner rotation time 30 seconds Spin coating atmosphere Under nitrogen atmosphere Heating condition Under nitrogen atmosphere 230 ° C. 1 hour The substrate on which the compound film has been formed is transferred into a vacuum deposition apparatus, and the degree of vacuum in the apparatus is 8.0 × 10 ⁻ using a turbo molecular pump. After evacuating to ⁴ Pa or less, gold was formed with a film thickness of 10 nm on the compound film by controlling the vapor deposition rate in the range of 0.2 to 0.5 kg / sec by vacuum vapor deposition. Subsequently, aluminum was laminated on gold with a film thickness of 80 nm by controlling the deposition rate in the range of 0.2 to 5.0 kg / sec. The degree of vacuum when forming the two-layer counter electrode was 0.5 to ³ × 10 ⁻³ Pa.
The charge mobility measurement sample thus prepared was measured by the TOF method according to the method described in (5-3. Measurement of charge mobility).
The results are shown in Table 1.

(Reference Example 2)
In forming the compound film, a coating solution containing the compound (H2) having the structure shown below and KF-96 manufactured by Shin-Etsu Silicone Co., Ltd. as a surface smoothing material is prepared, and spin coating is performed on the ITO pattern substrate under the following conditions. A sample for charge mobility measurement was prepared in the same manner as in Reference Example 1 except that a 2 μm-thick compound film was formed.

<Coating liquid for compound film formation>
Solvent Toluene Coating solution concentration (H2) 5.0% by weight
KF-96 0.023 wt%
<Film formation conditions>
Spinner speed 500rpm
Spinner rotation time 30 seconds Spin coating atmosphere Under nitrogen atmosphere Heating conditions Under nitrogen atmosphere 230 ° C. 1 hour Table 1 shows the measurement results of the prepared charge mobility measurement samples.

(Reference Example 3)
In forming the compound film, a coating solution containing the compounds (C1) and (C2) having the structure shown below is prepared, and is formed by spin coating on the ITO pattern substrate under the following conditions. A sample for measuring charge mobility was prepared in the same manner as in Reference Example 1 except that the compound film was formed.

<Coating liquid for compound film formation>
Solvent Chloroform Coating solution concentration (C1) 2.1 wt%
(C2) 6.3% by weight
<Film formation conditions>
Spinner speed 300rpm
Spinner rotation time 30 seconds Spin coating atmosphere In the air Heating conditions Under reduced pressure (0.1 MPa) 130 ° C. 1 hour Table 1 shows the measurement results of the prepared charge mobility measurement samples.
(Reference Example 4)
In forming the compound film, a coating solution containing the compounds (C1) and (C2) was prepared, and the film was formed by spin coating on the ITO pattern substrate under the following conditions to form a compound film having a thickness of 2 μm. Produced a sample for charge mobility measurement in the same manner as in Reference Example 1.

<Coating liquid for compound film formation>
Solvent Chloroform Coating solution concentration (C1) 6.3% by weight
(C2) 2.1 wt%
<Film formation conditions>
Spinner speed 300rpm
Spinner rotation time 30 seconds Spin coating atmosphere In the air Heating conditions Under reduced pressure (0.1 MPa) 130 ° C. 1 hour Table 1 shows the measurement results of the prepared charge mobility measurement samples.
(Reference Example 5)
In forming the compound film, a coating solution containing the compounds (C3) and (C4) having the structure shown below was prepared, and was formed by spin coating on the ITO pattern substrate under the following conditions. A sample for measuring charge mobility was prepared in the same manner as in Reference Example 1 except that the compound film was formed.

<Coating liquid for compound film formation>
Solvent Chloroform Coating solution concentration (C3) 2.1 wt%
(C4) 6.3 wt%
<Film formation conditions>
Spinner speed 300rpm
Spinner rotation time 30 seconds Spin coating atmosphere In the air Heating conditions Under reduced pressure (0.1 MPa) 130 ° C. 1 hour Table 1 shows the measurement results of the prepared charge mobility measurement samples.

(Reference Example 6)
In forming the compound film, a coating solution containing the compounds (C3) and (C4) was prepared, and the film was formed by spin coating on the ITO pattern substrate under the following conditions to form a compound film having a thickness of 2 μm. Produced a sample for charge mobility measurement in the same manner as in Reference Example 1.
<Coating liquid for compound film formation>
Solvent Chloroform Coating solution concentration (C3) 6.3 wt%
(C4) 2.1 wt%
<Film formation conditions>
Spinner speed 300rpm
Spinner rotation time 30 seconds Spin coating atmosphere In the air Heating conditions Under reduced pressure (0.1 MPa) 130 ° C. 1 hour Table 1 shows the measurement results of the prepared charge mobility measurement samples.

(Reference Example 7)
In forming the compound film, a coating solution containing the compound (C5) having the structure shown below is prepared, and formed on the ITO pattern substrate by spin coating under the following conditions to form a compound film having a thickness of 2 μm. Otherwise, a sample for measuring charge mobility was prepared in the same manner as in Reference Example 1.

<Coating liquid for compound film formation>
Solvent Chloroform Coating solution concentration 8.4% by weight
<Film formation conditions>
Spinner speed 300rpm
Spinner rotation time 30 seconds Spin coating atmosphere In the air Heating conditions Under reduced pressure (0.1 MPa) 130 ° C. 1 hour Table 1 shows the measurement results of the prepared charge mobility measurement samples.

(Reference Example 8)
In forming a compound film, Alq ₃ (C6) is deposited by controlling the deposition rate within a range of 0.8 to 1.2 liters / second by a vacuum deposition method and laminating it on the ITO pattern substrate to a thickness of 2 μm. A sample for charge mobility measurement was prepared in the same manner as in Reference Example 1 except that a film was formed.

  Table 1 shows the measurement results of the produced charge mobility measurement sample.

[Production of organic electroluminescence device]
Example 1
On the ITO patterning substrate prepared in the same manner as in Reference Example 1, first, an arylamine polymer represented by the following structural formula (H3), 4-isopropyl-4′-methyldiphenyliodonium tetrakis (penta) represented by the structural formula (A1). A coating solution for forming a hole injection layer containing fluorophenyl) borate and ethyl benzoate was prepared. This coating solution was formed by spin coating on the anode under the following conditions to obtain a hole injection layer having a thickness of 30 nm.

<Coating liquid for hole injection layer formation>
Solvent Ethyl benzoate Coating solution concentration H3: 2.0% by weight
A1: 0.4% by weight
<Film formation conditions for hole injection layer 3>
Spinner speed 1500rpm
Spinner rotation time 30 seconds Spin coating atmosphere In-air heating condition In-air 230 ° C. 1 hour Subsequently, a hole transport layer forming coating solution containing (H1) was prepared, and film formation was performed by spin coating under the following conditions. A hole transport layer having a thickness of 20 nm was formed by polymerization by heating.

<Coating liquid for hole transport layer formation>
Solvent Cyclohexylbenzene Coating solution concentration 1.0% by weight
<Film formation conditions for hole transport layer 4>
Spinner speed 1500rpm
Spinner rotation time 120 seconds Spin coating atmosphere Heating condition in nitrogen 230 ° C., 1 hour, in nitrogen Next, compounds (C1) and (C2) represented by the following structural formula and (D1) having the structure shown below are included. A light-emitting layer-forming coating solution was prepared, film-formed by spin coating under the following conditions, and heated to form a light-emitting layer having a thickness of 60 nm.

<Light emitting layer forming coating solution>
Solvent Cyclohexylbenzene Coating solution concentration C1: 1.25% by weight
C2: 3.75% by weight
D1: 0.50% by weight
<Film formation conditions of the light emitting layer 5>
Spinner speed 1500rpm
Spinner rotation time 120 seconds Spin coat atmosphere In nitrogen Heating condition 130 ° C., 1 hour, under reduced pressure (0.1 MPa)
Here, the substrate on which the light-emitting layer has been formed is transferred into a vacuum deposition apparatus, exhausted until the degree of vacuum in the apparatus becomes 2.0 × 10 ⁻⁴ Pa or less, and then the organic compound (C5) is subjected to vacuum deposition. The deposition rate was controlled in the range of 0.8 to 1.2 liters / second and laminated on the light emitting layer to obtain an electron transport layer having a thickness of 20 nm.

Here, the element that has been vapor-deposited up to the electron transport layer is once taken out and placed in another vapor deposition apparatus, and a 2 mm-wide stripe shadow mask is orthogonal to the ITO stripe of the anode 2 as a mask for cathode vapor deposition. The device was brought into close contact with the element and evacuated until the degree of vacuum in the apparatus became 2.3 × 10 ⁻⁴ Pa or less.
As an electron injection layer, lithium fluoride (LiF) was first formed on the electron transport layer 7 at a deposition rate of 0.1 kg / second and a film thickness of 0.5 nm using a molybdenum boat. The degree of vacuum at the time of vapor deposition was 2.6 × 10 ⁻⁴ Pa. Next, aluminum was similarly heated with a molybdenum boat as a cathode, and the deposition rate was controlled within a range of 1.0 to 4.9 liters / second to form an aluminum layer having a thickness of 80 nm. The degree of vacuum at the time of vapor deposition was 2.6 × 10 ⁻⁴ Pa. The substrate temperature during the above two-layer deposition was kept at room temperature.

Subsequently, in order to prevent the element from being deteriorated by moisture in the atmosphere during storage, a sealing process was performed by the method described below.
In a nitrogen glove box, a photocurable resin 30Y-437 (manufactured by Three Bond) is applied to the outer periphery of a 23 mm × 23 mm size glass plate with a width of about 1 mm, and a moisture getter sheet (manufactured by Dynic) is applied to the center. Was installed. On this, the board | substrate which complete | finished cathode formation was bonded together so that the vapor-deposited surface might oppose a desiccant sheet. Then, only the area | region where the photocurable resin was apply | coated was irradiated with ultraviolet light, and resin was hardened.

As described above, an organic electroluminescent element having a light emitting area portion having a size of 2 mm × 2 mm was obtained. Table 2 shows the characteristics of this element.
(Comparative Example 1)
In Example 1, an organic electroluminescent device was produced in the same manner as in Example 1 except that (H2) was used instead of (H1) to form a 15 nm thick hole transport layer.

Table 2 shows the characteristics of the obtained organic electroluminescent element.
(Comparative Example 2)
In Example 1, an organic electroluminescent element was produced in the same manner as in Example 1 except that Alq ₃ (C6) was used instead of (C5) to form an electron transport layer having a thickness of 20 nm.
Table 2 shows the characteristics of the obtained organic electroluminescent element.

(Comparative Example 3)
In Example 1, a coating solution for forming a light emitting layer shown below is prepared using (C1), (C2), and (D1), a film is formed by spin coating under the following conditions, and heated to form a film. An organic electroluminescent element was produced in the same manner as in Example 1 except that a light emitting layer having a thickness of 60 nm was formed.

<Light emitting layer forming coating solution>
Solvent Cyclohexylbenzene Coating solution concentration C1: 3.75% by weight
C2: 1.25% by weight
D1: 0.50% by weight
<Film formation conditions of the light emitting layer 5>
Spinner speed 1500rpm
Spinner rotation time 120 seconds Spin coat atmosphere In nitrogen Heating condition 130 ° C., 1 hour, under reduced pressure (0.1 MPa)
Table 2 shows the characteristics of the obtained organic electroluminescent element.

  As shown in Table 2, it can be seen that the organic electroluminescent element of the present invention has a good balance of voltage, efficiency and life.

(Example 2)
In Example 1, a light emitting layer forming coating solution shown below was prepared using (C3), (C4), (D1), and (D2), and film formation was performed by spin coating under the following conditions. Thus, an organic electroluminescent element was produced in the same manner as in Example 1 except that a light emitting layer having a thickness of 60 nm was formed.

<Light emitting layer forming coating solution>
Solvent Cyclohexylbenzene Coating solution concentration C3: 1.25 wt%
C4: 3.75% by weight
D1: 0.25% by weight
D2: 0.35% by weight
<Film formation conditions of the light emitting layer 5>
Spinner speed 1500rpm
Spinner rotation time 120 seconds Spin coat atmosphere In nitrogen Heating condition 130 ° C., 1 hour, under reduced pressure (0.1 MPa)
Table 3 shows the characteristics of the obtained organic electroluminescent element.

(Comparative Example 4)
In Example 2, an organic electroluminescent element was produced in the same manner as in Example 2 except that (H2) was used instead of (H1) to form a 15 nm-thick hole transport layer.
Table 3 shows the characteristics of the obtained organic electroluminescent element.
(Comparative Example 5)
In Example 2, an organic electroluminescent element was produced in the same manner as in Example 2 except that Alq ₃ (C6) was used instead of (C5) to form an electron transport layer having a thickness of 20 nm.

Table 3 shows the characteristics of the obtained organic electroluminescent element.
(Comparative Example 6)
In Example 2, the following light emitting layer forming coating solution was prepared using (C3), (C4), (D1), and (D2), and film formation was performed by spin coating under the following conditions, followed by heating. Thus, an organic electroluminescent element was produced in the same manner as in Example 2 except that a light emitting layer having a thickness of 60 nm was formed.

<Light emitting layer forming coating solution>
Solvent Cyclohexylbenzene Coating solution concentration C3: 3.75% by weight
C4: 1.25% by weight
D1: 0.25% by weight
D2: 0.35% by weight
<Film formation conditions of the light emitting layer 5>
Spinner speed 1500rpm
Spinner rotation time 120 seconds Spin coat atmosphere In nitrogen Heating condition 130 ° C., 1 hour, under reduced pressure (0.1 MPa)
Table 3 shows the characteristics of the obtained organic electroluminescent element.

  As shown in Table 3, it can be seen that the organic electroluminescent element of the present invention has a good balance of voltage, efficiency and life.

  The present invention relates to various fields in which organic electroluminescent elements are used, for example, light sources (for example, light sources of copiers, flat panel displays (for example, for OA computers and wall-mounted televisions) and surface light emitters). It can be suitably used in the fields of liquid crystal displays and backlights for measuring instruments), display panels, marker lamps and the like.

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 device comprising an anode, a first organic layer, a light emitting layer, a third organic layer, a second organic layer, and a cathode in this order,
The first organic layer or the light emitting layer is formed by a wet film formation method,
An organic electroluminescence device satisfying the following formulas (1), (2) , (3) and (5) .
μ (h1) / μ (e1) ≧ 5 (1)
μ (h2) ≧ 1.0 × 10 ⁻⁴ (2)
μ (e2) ≧ 1.0 × 10 ⁻⁴ (3)
μ (e3) ≧ 1.0 × 10 ⁻⁴ (5)
(In the above formula, μ (h1) is the hole mobility (cm ² / V · s) of the light emitting layer,
μ (e1) is the electron mobility (cm ² / V · s) of the light emitting layer,
μ (h2) is the hole mobility (cm ² / V · s) of the first organic layer,
μ (e2) is the electron mobility (cm ² / V · s) of the second organic layer,
μ (e3) is the electron mobility (cm ² / V · s) of the third organic layer
Represents. The charge mobility is a value obtained when the square root of the electric field strength is 500 (V / cm) ^0.5 . )   The organic electroluminescent device according to claim 1, wherein the light emitting layer is formed by a wet film forming method.   The organic electroluminescent element according to claim 1 or 2, wherein the first organic layer contains an insolubilized polymer formed by insolubilizing a compound having an insolubilizing group. The organic electroluminescent element according to claim 3, wherein the compound having an insolubilizing group is a compound having a partial structure represented by the following formula (4).

The excitation energy of the third organic layer, than the excitation energy of the light emitting layer, and wherein the large organic electroluminescent device according to any one of claims 1-4. Characterized in that it comprises an organic electroluminescent element according to any one of claims 1 to 5 organic EL display. An organic EL illumination comprising the organic electroluminescent element according to any one of claims 1 to 5 . Characterized in that it comprises an organic electroluminescent element according to any one of claims 1 to 5 organic EL signal device.

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