JP5499482B2 - Organic electroluminescence device, organic EL display and organic EL lighting - Google Patents

Description

  The present invention relates to an organic electroluminescent device having a hole injection layer, a hole transport layer, and a light emitting layer formed by a wet film forming method.

In recent years, an electroluminescent element (organic electroluminescent element) using an organic thin film has been developed.
An organic electroluminescent element is usually formed by laminating a plurality of organic layers between an anode and a cathode, and the organic layer includes a hole injection layer, a hole transport layer, a light emitting layer, a hole blocking layer, an electron. Examples include a transport layer. As a method for forming these organic layers, a vacuum deposition method, a wet film formation method, or the like is used. However, in order to manufacture a large-area display, it is preferable to use a wet film formation method.

For example, a technique for forming a polymer hole transport material by wet film formation on a hole injection layer formed on an anode is disclosed (for example, see Patent Document 1). Further, a technique for forming a light emitting layer by wet-depositing a low molecular light emitting material is disclosed (for example, see Patent Document 2).
However, devices manufactured using these wet film forming methods, particularly devices having a light emitting layer formed by wet film formation of a low-molecular light emitting material, have a reduced luminance when driven, and a long-life device can be obtained. There was no problem.

JP 2007-123257 A JP 2006-190759 A

  The present invention relates to an organic electroluminescent device having a hole injection layer obtained by wet film formation of a polymer hole transport material and a light emitting layer obtained by wet film formation of a low molecular light emitting material. It is an object to provide an element having a small lifetime and a long lifetime.

As a result of intensive studies by the present inventors, holes provided between a hole injection layer obtained by wet film formation of a polymer hole transport material and a light emitting layer obtained by wet film formation of a low molecular light emitting material It has been found that the above problem can be solved by forming the transport layer by crosslinking a crosslinkable compound, and the present invention has been achieved.
That is, the present invention relates to an organic electroluminescent device having an anode, a cathode, and a hole injection layer, a hole transport layer, and a light emitting layer in this order between the anode and the cathode. The hole transport material is a layer formed by wet film formation, the hole transport layer is a layer formed by crosslinking a crosslinkable compound, and the light emitting layer is formed by wet forming a low molecular weight light emitting material. The present invention resides in an organic electroluminescent device characterized by being a layer formed by film formation.

  According to the present invention, in an organic electroluminescent device having a hole injection layer obtained by wet film formation of a polymer hole transport material and a light emitting layer obtained by wet film formation of a low molecular light emitting material, It is possible to provide a device having a long lifetime with little reduction in luminance and improved driving voltage.

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

The description of the constituent requirements described below is an example (representative example) of the embodiment of the present invention, and the contents are not specified.
The organic electroluminescent device of the present invention includes an anode, a cathode, and a hole injection layer, a hole transport layer, and a light emitting layer in this order between the anode and the cathode. A layer formed by wet film formation of a polymer hole transport material, the hole transport layer is a layer formed by crosslinking a crosslinkable compound, and the light emitting layer is a low molecular light emitting material. It is a layer formed by wet film formation.

Hereinafter, the organic electroluminescent element of the present invention will be described with reference to FIG. The organic electroluminescent element of the present invention has at least a hole injection layer, a hole transport layer and a light emitting layer between the anode and the cathode, but may or may not have other layers. .
[1] Substrate
The substrate serves as a support for the organic electroluminescence device, and quartz or glass plates, metal plates or metal foils, plastic films or sheets are used. In particular, a glass plate or a transparent synthetic resin plate such as polyester, polymethacrylate, polycarbonate, or polysulfone 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.

[2] Anode
The anode plays a role of hole injection into a layer (hole injection layer or organic light emitting layer) on the organic light emitting layer side described later. This anode is usually made of metal such as aluminum, gold, silver, nickel, palladium, platinum, metal oxide such as oxide of indium and / or tin, metal halide such as copper iodide, carbon black, or poly It is composed of conductive polymers such as (3-methylthiophene), polypyrrole, and polyaniline. In general, the anode 2 is often formed by sputtering, vacuum deposition, or the like. Also, in the case of fine metal particles such as silver, fine particles such as copper iodide, carbon black, conductive metal oxide fine particles, conductive polymer fine powder, etc., it is dispersed in an appropriate binder resin solution and placed on the substrate. An anode can also be formed by coating. 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 (Applied Physics Letters, 1992, Vol.60, pp.2711). The anode can be formed by stacking different materials.

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

  In addition, the surface of the anode is treated with ultraviolet (UV) / ozone, oxygen plasma, or argon plasma for the purpose of removing impurities adhering to the anode and adjusting the ionization potential to improve the hole injection property. Is preferred. A known anode buffer layer may be inserted between the hole injection layer and the anode for the purpose of further improving the efficiency of hole injection and improving the adhesion of the entire organic layer to the anode. .

[3] Hole injection layer
In the present invention, the hole injection layer is a layer formed by wet film formation of a polymer hole transport material. The hole injection layer may contain an electron-accepting compound, a low-molecular hole-transporting material, a binder resin, a coating property improving agent, and the like in addition to the polymer hole-transporting material.
In the present invention, the wet film formation is a method of forming a film by appropriately dispersing or dissolving a material for forming an organic layer in a solvent, for example, a spin coating method, a dip coating method, or a die coating method. , Bar coating method, blade coating method, roll coating method, spray coating method, capillary coating method, ink jet method, screen printing method, gravure printing method, flexographic printing method, and the like.

Specifically, the polymer hole transport material is preferably a polymer material having a hole transport property that is usually used for a hole injection layer of an organic electroluminescence device.
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 3. Examples of polymer hole transport materials 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, Silanamine derivatives, phosphamine derivatives, quinacridone derivatives, polyaniline derivatives, polypyrrole derivatives, polyphenylene vinylene derivatives, polythienylene vinylene derivatives, polyquinoline derivatives, polyquinoxaline derivatives, polyaniline derivatives, polyfluorene derivatives, polythiophene derivatives, aromatic polyamine derivatives, polysilane derivatives, Examples thereof include polypyrrole derivatives, polyparaphenylene vinylene derivatives, and carbon.

In the present invention, the derivative includes, for example, an aromatic amine derivative and a compound having an aromatic amine as a main skeleton, for example.
Among them, a polymer hole transport material having an aromatic amine is preferable, and a polymer hole transport material containing an aromatic tertiary amino group as a constituent unit in the main skeleton is particularly preferable. The weight average molecular weight of the polymeric hole transport material used in the present invention is preferably 1,000 or more and 1,000,000 or less. The polymer hole transport material may be used alone or in combination of two or more of such compounds. When two or more types of polymer hole transport materials are used, the combination thereof is arbitrary, but one or more polymer hole transport materials containing an aromatic tertiary amino group as a constituent unit in the main skeleton It is preferable to use one or more other hole transporting compounds in combination.

  Hereinafter, Formula (2) which is an example of a preferable polymeric hole transport material will be described.

(In the formula (2), Ar ^{44 to} Ar ⁴⁸ each independently represents a divalent aromatic ring group which may have a substituent, and R ^{31 to} R ³² each independently represents a substituent. And X is selected from a direct bond or the following linking group, wherein “aromatic ring group” means “derived from an aromatic hydrocarbon ring” Including "group" and "group derived from an aromatic heterocycle")

(In formula (3), Ar ⁴⁹ represents a divalent aromatic ring group which may have a substituent, and Ar ⁵⁰ represents a monovalent aromatic ring group which may have a substituent. .)
In the general formula (2), Ar ^{44 to} Ar ⁴⁸ are each preferably a group derived from a divalent benzene ring, naphthalene ring, anthracene ring or biphenyl group which may each independently have a substituent, A group derived from a benzene ring is preferred. Examples of the substituent include a halogen atom, an alkyl group, an alkenyl group, an alkoxycarbonyl group, an alkoxy group, an aryloxy group, a dialkylamino group, and the like. Of these, an alkyl group having 1 to 3 carbon atoms is preferable. Most preferably, Ar ^{44 to} Ar ⁴⁸ are each an unsubstituted aromatic ring group.

R ³¹ and R ³² are preferably each independently a phenyl group, naphthyl group, anthryl group, pyridyl group, triazyl group, pyrazyl group, quinoxalyl group, thienyl group, or biphenyl group, which may have a substituent. Preferably a phenyl group, a naphthyl group or a biphenyl group, more preferably a phenyl group. Examples of the substituent include a group in which an aromatic ring in Ar ⁴⁴ to Ar ⁴⁸ may have include the same groups as previously described.

In the general formula (3), Ar ⁴⁹ is a divalent aromatic ring group which may have a substituent, preferably an aromatic hydrocarbon ring group from the viewpoint of hole transportability. Includes an optionally substituted divalent benzene ring, naphthalene ring, anthracene ring-derived group, biphenylene group, and terphenylene group. Further, examples of the substituent include a group in which an aromatic ring may have at Ar ⁴⁴ to Ar ^48, include the same groups as previously described. Of these, an alkyl group having 1 to 3 carbon atoms is preferable.

Ar ⁵⁰ is an aromatic ring group which may have a substituent, preferably an aromatic hydrocarbon ring group from the viewpoint of hole transportability, and specifically, phenyl which may have a substituent. Group, naphthyl group, anthryl group, pyridyl group, triazyl group, pyrazyl group, quinoxalyl group, thienyl group, biphenyl group and the like. As this substituent, the group similar to the group mentioned above is mentioned as a group which the aromatic ring in Ar < ⁴⁴ > -Ar < ⁴⁸ > of General formula (2) may have.

  The polymer hole transport material used in the hole injection layer of the present invention may be a crosslinkable compound such as the hole transport layer described in detail below, that is, the hole injection layer is a crosslinkable compound. It may be a layer obtained by crosslinking.

Specific examples of the aromatic tertiary amine polymer compound having a repeating unit represented by the formula (2) include those described in International Publication No. 2005/089024.
In addition, as a polymer hole transport material, 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.

Next, the electron accepting compound will be described. 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; No.-251067), high-valence inorganic compounds such as ammonium peroxodisulfate; cyano compounds such as tetracyanoethylene; aromatic boron compounds such as tris (pendafluorophenyl) borane (JP-A-2003-31365); fullerenes Derivatives; iodine; sulfonate ions such as polystyrene sulfonate ions, alkylbenzene sulfonate ions, camphor sulfonate ions, and the like. These electron-accepting compounds can improve the conductivity of the hole injection layer by oxidizing the hole transport material. The content of the electron-accepting compound with respect to the polymer hole transport material is usually 0.1% by weight or more, preferably 1% by weight or more. However, it is usually 100% by weight or less, preferably 40% by weight or less.

  Examples of the low molecular hole transport material include conventionally known compounds that have been used as a hole transport material for organic electroluminescence devices. Examples include aromatic diamine compounds, aromatic triamine compounds, benzylphenyl compounds, compounds in which tertiary amines are linked by a fluorene group, hydrazone compounds, silazane compounds, silanamine derivatives, phosphamine derivatives, quinacridone compounds, phthalocyanine derivatives, or porphyrin derivatives. It is done.

In order to form the hole injection layer by wet film formation, a coating solution in which a polymer hole transport material is dissolved or dispersed in a solvent is usually prepared and used for wet film formation.
The concentration of the polymer hole transporting material in the coating solution for forming the 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 in terms of film thickness uniformity. It is preferably 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.

  Examples of the solvent include ether solvents, ester solvents, aromatic hydrocarbon solvents, and amide solvents, and it is particularly preferable to use hydrophobic solvents such as these. Specifically, examples of the ether solvent include aliphatic ethers such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol-1-monomethyl ether acetate (PGMEA); 1,2-dimethoxybenzene, 1, 3 -Aromatic ethers such as dimethoxybenzene, anisole, phenetole, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2,3-dimethylanisole, 2,4-dimethylanisole; ethyl acetate, n-butyl acetate, Aliphatic esters such as ethyl lactate and n-butyl lactate; Aromatic esters such as phenyl acetate, phenyl propionate, methyl benzoate, ethyl benzoate, propyl benzoate, n-butyl benzoate; benzene, toluene, xylene, etc. Aromatic carbonization Motokei solvent; N, N-dimethylformamide, N, N-amide solvents dimethylacetamide and the like; dimethyl sulfoxide and the like. Any one of these may be used alone, or two or more thereof may be used in any combination and ratio.

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.
After preparing the coating solution, the coating solution is usually formed on the anode by wet film formation. The temperature during film formation is preferably 10 to 50 ° C., and the relative humidity is preferably 0.01 ppm to 80%.

Examples of the heating means used in the heating step include a clean oven, a hot plate, an infrared ray, a halogen heater, and microwave irradiation. 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 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 coating solution, it is preferable that at least one type is 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, it is preferable to heat at 120 ° C. or higher, preferably 410 ° C. or lower, more preferably 300 ° C. or lower in the heating step.

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 coating solution and sufficient insolubilization of the coating film does not occur, but it is preferably 10 seconds or longer and usually 180 minutes or shorter. 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.
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.

[4] Hole transport layer
The hole transport layer is usually formed on the hole injection layer. In the present invention, the hole transport layer is formed by crosslinking a crosslinkable compound.
The crosslinkable compound is a compound having a crosslinking group, and forms a polymer by crosslinking. The crosslinkable compound may be any of a monomer, an oligomer, and a polymer. The crosslinkable compound may have only 1 type, and may have 2 or more types by arbitrary combinations and ratios.

Examples of crosslinking groups include groups derived from cyclic ethers such as oxetane and epoxy; groups derived from unsaturated double bonds such as vinyl, trifluorovinyl, styryl, acryl, methacryloyl and cinnamoyl; benzo Examples include groups derived from cyclobutene.
The number of crosslinking groups in the monomer, oligomer or polymer having a crosslinking group is not particularly limited, but is usually less than 2.0, preferably not more than 0.8, more preferably not more than 0.5 per unit charge transport unit. Is preferred. This is to keep the relative permittivity within a suitable range. Moreover, when the number of crosslinking groups is too large, reactive active species are generated, which may adversely affect other materials. Here, when the material forming the crosslinkable polymer is a monomer body, the unit charge transport unit is a monomer body itself, and indicates a skeleton (main skeleton) excluding a crosslinking group. Even when other types of monomers are mixed, the main skeleton of each monomer is shown. When the material forming the crosslinkable polymer is an oligomer or polymer, in the case of repeating a structure in which conjugation is broken organically, the repeated structure is defined as a unit charge transport unit. In the case of a structure in which conjugation is widely connected, a minimum repeating structure exhibiting charge transporting property or a monomer structure is shown. Examples include polycyclic aromatics such as naphthalene, anthracene, phenanthrene, tetracene, chrysene, pyrene, perylene, fluorene, triphenylene, carbazole, triarylamine, tetraarylbenzidine, 1,4-bis (diarylamino) benzene, and the like. It is done.

As the crosslinkable compound, a hole transporting compound having a crosslinkable group (crosslinkable hole transporting compound) is preferably used. 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. Particularly preferred are triphenylamine derivatives. 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 an alternating copolymer, a random polymer, a block polymer, or a graft copolymer. Further, it may be a polymer having a branched main chain and three or more terminal portions, or a so-called dendrimer.

With respect to these hole transporting compounds, those in which a crosslinkable group is bonded to a main chain or a side chain can be mentioned. In particular, the crosslinkable group is preferably bonded to the main chain via a linking group such as an alkylene group.
In particular, as the hole transporting compound, a polymer containing a repeating unit having a crosslinkable group is preferable, and among them, it is preferable to have a polyarylamine derivative or a polyarylene derivative in the repeating unit. A polymer having a repeating unit in which a crosslinkable group is bonded directly or via a linking group to (II) or formulas (III-1) to (III-3) is preferred.

<Formula (II)>
A polyarylamine derivative-based polymer containing a repeating unit represented by the following formula (II) is preferred. In particular, a polymer composed of a repeating unit represented by the following formula (II) is preferred. 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 polymer which has is mentioned.
<Formulas (III-1) to (III-3)>
As a polyarylene derivative, the polymer which has a repeating unit which consists of following formula (III-1) and / or 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.
In the case of a low molecular weight material (compound consisting of a single molecular weight), the molecular weight of the crosslinkable compound is usually 5000 or less, preferably 2500 or less, preferably 300 or more, more preferably 500 or more. In the case of a polymer material (polymer containing a repeating unit), the weight average molecular weight is usually 10,000 or more, preferably 15,000 or more, usually 2,000,000 or less, preferably 1,000,000 or less, and the number average molecular weight is usually 3,000 or more, preferably 6,000 or more, usually 1000000 or less, preferably 500000 or less.

In the hole transport layer in the present invention, monomers, oligomers and polymers having no crosslinking group can be used in combination with the crosslinking compound.
Although the specific example of a crosslinkable compound is given to the following, it is not limited to this. Moreover, as a specific example, the crosslinkable hole transport compound etc. which are used in the Example explained in full detail below other than the compound as described below are mentioned, for example.

In order to form a hole transport layer by crosslinking a crosslinkable compound, usually, a coating solution in which the crosslinkable compound is dissolved or dispersed in a solvent is prepared, and the film is crosslinked by wet film formation.
In addition to the crosslinkable compound, the coating solution may contain an additive that accelerates the crosslinking reaction. Examples of additives that promote the crosslinking reaction include polymerization initiators and polymerization accelerators such as alkylphenone compounds, acylphosphine oxide compounds, metallocene compounds, oxime ester compounds, azo compounds, onium salts; condensed polycyclic hydrocarbons, And photosensitizers such as porphyrin compounds and diaryl ketone compounds. Further, it may contain a coating property improving agent such as a leveling agent and an antifoaming agent; an electron accepting compound: a binder resin, and the like.

The solvent used for the coating solution is the same as that exemplified as the solvent for forming the hole injection layer. In the coating solution, the crosslinkable compound is usually 0.01% by weight or more, preferably 0.05% by weight or more, more preferably 0.1% by weight or more, usually 50% by weight or less, preferably 20% by weight or less, more preferably. Contains 10% by weight or less.
After the coating liquid is formed on the lower layer (usually on the hole injection layer), the crosslinkable compound is crosslinked and polymerized by heating and / or irradiation with electromagnetic energy such as light. Conditions such as temperature and humidity during film formation are the same as those during film formation of the hole injection layer.

  The heating method after film formation is not particularly limited, and examples thereof include heat drying and reduced pressure drying. As conditions for the heat drying, the layer 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 laminated body having a deposited layer 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.

  In the case of irradiation with electromagnetic energy such as light, a method of irradiating directly using an ultraviolet / visible / infrared light source such as an ultra-high pressure mercury lamp, a high-pressure mercury lamp, a halogen lamp or an infrared lamp, or the above-mentioned light source is incorporated. Examples include a mask aligner and a method of irradiation using a conveyor type light irradiation device. In electromagnetic energy irradiation other than light, for example, there is a method of irradiation using a device that irradiates a microwave generated by a magnetron, a so-called microwave oven. 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.

Heating and irradiation of electromagnetic energy such as light may be performed individually or in combination. When combined, the order of implementation is not particularly limited.
In order to reduce the amount of moisture contained in the layer and / or moisture adsorbed on the surface after implementation, the electromagnetic energy irradiation including heating and light is preferably performed in an atmosphere containing no moisture such as a nitrogen gas atmosphere. For the same purpose, when combined with heating and / or irradiation with electromagnetic energy such as light, it is particularly preferable to perform at least the step immediately before the formation of the organic light emitting layer in an atmosphere containing no moisture such as a nitrogen gas atmosphere.

[5] Light emitting layer
In the present invention, the light emitting layer is a layer formed by wet film formation of a low molecular light emitting material. The light emitting layer is preferably a layer containing this low molecular light emitting material as a dopant material and further containing a low molecular charge transport material as a host material. Here, the low molecular light emitting material and the low molecular charge transporting material referred to in the present invention have a molecular weight of 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. The compound is preferably 200 or more, more preferably 300 or more, and still more preferably 400 or more. If the molecular weight is below the lower limit, the heat resistance is remarkably reduced, gas is generated, the film quality is deteriorated when the film is formed, or the morphology of the organic electroluminescent device is changed due to migration or the like. This is not preferable. When the molecular weight exceeds the upper limit, it is not preferable because it is difficult to purify the organic compound or it takes time to dissolve in the solvent.

Any known material can be applied as the low-molecular light-emitting material. 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.
Examples of fluorescent dyes (fluorescent materials) that emit blue light include naphthalene, perylene, pyrene, anthracene, coumarin, p-bis (2-phenylethenyl) benzene, and derivatives thereof. Examples of the green fluorescent dye include quinacridone derivatives and coumarin derivatives. Examples of yellow fluorescent dyes include rubrene and perimidone derivatives. Red fluorescent dyes include DCM (4- (dicyanomethylene) -2-methyl-6- (p-dimethylaminostyryl) -4H-pyran) compounds, benzopyran derivatives, rhodamine derivatives, benzothioxanthene derivatives, azabenzothioxanthene, etc. Can be mentioned.

  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.

Only one kind of low molecular light emitting material may be used, or two or more kinds may be used in combination.
The low molecular charge transporting material used as the host material may be a compound used as a host material for the light emitting layer. For example, a carbazole compound, a triarylamine compound, a phenylanthracene compound, a fused arylene Starburst compound, condensed imidazole compound, azepine compound, condensed triazole compound, propeller arylene compound, monotriarylamine compound, arylbenzidine compound, triarylboron compound, indole compound, Examples include indolizine compounds, pyrene compounds, dibenzoxazole (or dibenzothiazole) compounds, bipyridyl compounds, pyridine compounds, and the like.

  Among these, from the point of excellent light emission characteristics when using an organic electroluminescent device, a carbazole compound, a triarylamine compound, a phenanthroline compound, an oxadiazole compound, a starburst compound of a condensed ring arylene, A condensed ring imidazole compound, a propeller type arylene compound, a monotriarylamine type compound, an indole compound, an indolizine compound, a bipyridyl compound, a pyridine compound and the like are preferable.

More specifically, 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl, 4,4 ′, 4 ″ -tris (1-naphthylphenylamino) triphenylamine, 2, 2 ′, 7,7′-tetrakis- (diphenylamino) -9,9′-spirobifluorene, 2,5-bis (1-naphthyl) -1,3,4-oxadiazole (BND), 2, 5-bis (6 ′-(2 ′, 2 ″ -bipyridyl))-1,1-dimethyl-3,4-diphenylsilole (PyPySPyPy), bathophenanthroline (BPhen), 2,9-dimethyl-4,7- Diphenyl-1,10-phenanthroline (BCP, bathocuproin), 2- (4-biphenylyl) -5- (p-tertiarybutylphenyl) -1,3,4-oxadiazole (tBu-PBD), 4, And 4′-bis (9-carbazole) -biphenyl (CBP).

Only one type of low molecular charge transport material may be used, or two or more types may be used in combination.
In order to obtain a light emitting layer by depositing a low molecular light emitting material by wet film formation, a coating solution in which a low molecular light emitting material is dissolved or dispersed in a solvent is usually prepared, and the film is formed by wet film formation. The coating solution preferably contains a solvent in addition to a low molecular light emitting material, and further contains a low molecular charge transport material.

  As the solvent, those exemplified as the solvent used when the hole injection layer is formed into a wet film are also suitable. Further, the concentration of the low molecular light emitting material and the low molecular charge transport material in the coating solution is not limited as long as the effect of the present invention is not significantly impaired, but is usually 0.01% by weight or more, preferably 0.1% by weight. Above, 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 the concentration is too high, film thickness unevenness may occur, and if it is too low, defects may occur in the deposited layer.

  Further, the weight mixing ratio of the light emitting material / charge transporting material in the coating solution or in the light emitting layer is usually 0.1 / 99.9 or more, more preferably 0.5 / 99.5 or more, More preferably 1/99 or more, most preferably 2/98 or more, usually 50/50 or less, more preferably 40/60 or less, still more preferably 30/70 or less, and most preferably Is 20/80 or less.

In addition, the coating solution may contain various additives such as a leveling agent and an antifoaming agent, a binder resin, and the like.
After preparing the coating solution, the coating solution is wet-formed on the lower layer (usually on the hole transport layer). The film formation temperature is not limited as long as the effects of the present invention are not significantly impaired, but is preferably 10 ° C or higher, more preferably 13 ° C or higher, further preferably 16 ° C or higher, preferably 50 ° C or lower, and 40 ° C or lower. More preferably, it is 30 ° C. or less. This is for suppressing generation of crystals in the coating solution. The relative humidity is not limited as long as the effect of the present invention is not significantly impaired, but is usually 0.01 ppm or more, preferably 0.05 ppm or more, more preferably 0.1 ppm or more, and usually 80% or less, preferably 60% or less. More preferably, it is at most 15%, further preferably at most 1%, particularly preferably at most 100 ppm. If the relative humidity is too small, it may be difficult to control film forming conditions in the wet film forming method. On the other hand, if it is too large, moisture adsorption on the organic layer may be easily affected.

  The volume concentration of oxygen during film formation is not limited as long as the effect of the present invention is not significantly impaired, but is preferably 0.01 ppm or more, more preferably 0.05 ppm or more, and preferably 50% or less, more preferably 25. % Or less, more preferably 1% or less, particularly preferably 100 ppm or less, particularly preferably 10 ppm or less. An environment in which the oxygen concentration is too low is difficult to control. If the oxygen concentration is too high, oxygen diffuses inside the organic layer, which may adversely affect device characteristics.

In addition, the low molecular weight light emitting material in the light emitting layer of the present invention is a component that mainly emits light, and is usually 10 to 100%, preferably 20 of the light amount (unit: cd / m ² ) emitted from the organic electroluminescent element. -100%, more preferably 50-100%, most preferably 80-100%. Therefore, the light emitting layer of the present invention may contain some polymer light emitting material, but in that case, it does not mainly emit light. The light emitting layer of the present invention preferably contains no polymer light emitting material.

After the film formation, it is preferable to heat dry the light emitting layer. For this heat drying, a known heating means such as a hot plate, oven, electromagnetic wave heating or the like is used. In order to sufficiently obtain the effect of the heat treatment, it is preferable to perform the treatment at 60 ° C. or higher, and it is more preferable to perform the treatment at 100 ° C. or higher in order to reduce the residual water content. The heating time is usually about 1 minute to 8 hours.
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 thickness of the light emitting layer is too thin, defects may occur in the light emitting layer, and if it is too thick, the driving voltage of the organic EL element may increase.

As described above, in the present invention, the hole injection layer, the hole transport layer, and the light emitting layer may be laminated in this order, and other layers may be provided between these layers. The hole transport layer and the light emitting layer are preferably laminated adjacent to each other in this order.
[6] Hole blocking layer
A hole blocking layer may be provided on the light emitting layer. The hole blocking layer has a role of blocking holes moving from the anode from reaching the cathode and a role of efficiently transporting electrons injected from the cathode toward the light emitting layer.

  The physical properties required for the material constituting the hole blocking layer include high electron mobility, low hole mobility, large energy gap (difference between HOMO and LUMO), and excited triplet level (T1). It is expensive. As a material for the hole blocking layer satisfying such conditions, for example, bis (2-methyl-8-quinolinolato), (phenolato) aluminum, bis (2-methyl-8-quinolinolato), (triphenylsilanolato) Mixed ligand complexes such as aluminum, metal complexes such as bis (2-methyl-8-quinolato) aluminum-μ-oxo-bis- (2-methyl-8-quinolinato) aluminum binuclear metal complexes, distyrylbiphenyl derivatives Styryl compounds such as JP-A-11-242996 and triazole derivatives such as 3- (4-biphenylyl) -4-phenyl-5 (4-tert-butylphenyl) -1,2,4-triazole Kaihei 7-41759) and phenanthroline derivatives such as bathocuproine (Japanese Patent Laid-Open No. 10-79297). It is. Furthermore, compounds having at least one pyridine ring substituted at the 2,4,6-positions described in International Publication No. 2005-022962 are also preferable as the material for the hole blocking layer. In addition, the material of a hole-blocking layer may use only 1 type, and may use 2 or more types together by arbitrary combinations and ratios. There is no restriction | limiting in the formation method of a hole-blocking layer. Therefore, it can be formed by a wet film formation method, a vacuum deposition method, or other methods. A vacuum deposition method is preferred.

The thickness of the hole blocking 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.
[7] Electron transport layer
For example, an electron transport layer may be provided between the cathode and the light emitting layer. The electron transport 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. Is formed.

As the electron transporting compound used for the electron transport layer, usually, the electron injection efficiency from the cathode 6 or the electron injection layer 5 is high, and the injected electrons having high electron mobility can be efficiently transported. Use possible compounds. 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, and 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 Sele Zinc oxide and the like. In addition, only 1 type may be used for the material of an electron carrying 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 an electron carrying layer. Therefore, it can be formed by a wet film formation method, a vacuum deposition method, or other methods. A vacuum deposition method is preferred.
The thickness of the electron transport 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.

[8] Electron injection layer
The electron injection layer 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 is preferably a metal having a low work function. Examples include alkali metals such as sodium and cesium, and alkaline earth metals such as barium and calcium. The film thickness is usually 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. Further, for example, an ultra-thin insulating film (0.1 to 5 nm) formed of lithium fluoride (LiF), magnesium fluoride (MgF ₂ ), lithium oxide (Li ₂ O), cesium carbonate (II) (CsCO ₃ ), or the like. ) Is also an effective method for improving the efficiency of the device (Applied Physics Letters, 1997, Vol. 70, pp. 152; Japanese Patent Laid-Open No. 10-74586; IEEE Transactions on Electron Devices, 1997) , Vol. 44, pp. 1245; see SID 04 Digest, pp. 154, etc.).

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 5 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 5. FIG. Therefore, it can be formed by a wet film formation method, a vacuum deposition method, or other methods.

[9] Cathode
The cathode plays a role of injecting electrons into the layer on the light emitting layer side.
As the material of the cathode, it is possible to use the material used for the anode described above, but in order to perform electron injection efficiently, a metal having a low work function is preferable, 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. The material of the cathode 6 is
Only 1 type may be used 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.
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.

[10] Other layers
The organic electroluminescent element of 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 and the cathode in addition to the layers described above, and an arbitrary layer may be omitted.
[11] Electron blocking layer
The electron blocking layer prevents the electrons moving from the light emitting layer from reaching the hole transport layer and hole injection layer, thereby increasing the recombination probability of holes and electrons in the light emitting layer. There are a role of confining the excitons in the light emitting layer and a role of efficiently transporting holes injected from the hole transport layer and the hole injection layer in the direction of the light emitting layer. In particular, it is effective when a phosphorescent material or a blue light emitting material is used as the light emitting material.

  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 the electron blocking layer 8 include a copolymer of dioctylfluorene and triphenylamine typified by F8-TFB (described in 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 formation method, a vacuum deposition method, or other methods.
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, other components are provided in order from the cathode on the substrate 1.

Furthermore, the organic electroluminescent element of the present invention can be configured 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 of 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, and an anode and a cathode May be applied to a configuration in which are arranged in an XY matrix.
Each layer described above may contain components other than those described as materials unless the effects of the present invention are significantly impaired.

  The organic electroluminescent element of the present invention is used for organic EL displays and organic EL lighting. 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). An organic EL display and organic EL illumination can be formed by the method.

Examples The present invention will be described more specifically with reference to examples. However, the present invention is not limited to the description of the following examples unless it exceeds the gist.
Example 1
The organic electroluminescent element shown in FIG. 1 was produced.
Indium tin oxide (ITO) transparent conductive film deposited to a thickness of 120 nm on a glass substrate 1 having a size of 37.5 mm × 25 mm (thickness 0.7 mm) (manufactured by Sanyo Vacuum Co., Ltd., sputter film formation) Product) was patterned into a stripe with a width of 2 mm using a normal photolithography technique and hydrochloric acid etching to form an anode 2. 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.

  First, a hole injection layer composition containing a polymer hole transport material (P1, weight average molecular weight: 29400, number average molecular weight: 12600), an electron accepting compound (A1), and ethyl benzoate as a solvent represented by the following structural formula: A film coating solution was prepared in the air. This coating solution was formed on the anode 2 by the spin coating method under the following conditions and dried by heating to obtain a hole injection layer 3 having a thickness of 30 nm.

<Hole injection layer coating solution>
Solvent ethyl benzoate
Coating solution concentration P1: 2.0% by weight
A1: 0.8% by weight
<Film formation conditions>
Spinner speed 1500rpm
Spinner rotation time 30 seconds
Spin coat atmosphere In air
Heating and drying conditions In air, 230 ° C, 3 hours
Subsequently, the hole transport layer 4 was formed on the hole injection layer by the wet deposition method according to the following procedure. As a crosslinkable hole transport compound, a coating solution containing a compound represented by the following structural formula (H1) (weight average molecular weight: 17000, number average molecular weight: 8900) and toluene as a solvent is used, and spin coating is performed under the following conditions. A film was formed and crosslinked by heating to obtain a uniform hole transport layer 4 having a thickness of 20 nm.

<Hole transport layer coating solution>
Solvent Toluene
Coating solution concentration H1: 0.4% by weight
<Film formation conditions>
Spinner speed 1500rpm
Spinner rotation time 30 seconds
Spin coat atmosphere In nitrogen
Heating conditions In nitrogen, 230 ° C, 1 hour
Next, in forming the light emitting layer 5, the following organic compound (E1), (E2), an iridium complex (D1) as a low molecular light emitting material, and xylene as a solvent are prepared. Then, a film was formed on the hole transport layer 4 by a spin coating method under the conditions shown below, followed by drying by heating to obtain the light emitting layer 5 with a film thickness of 50 nm.

<Light emitting layer coating solution>
Solvent xylene
Coating solution concentration E1: 1.0% by weight
E2: 1.0% by weight
D1: 0.1% by weight
<Film formation conditions>
Spinner speed 1500rpm
Spinner rotation time 30 seconds
Spin coat atmosphere In nitrogen
Heating and drying conditions in nitrogen, 130 ° C, 1 hour
Here, the substrate on which the light emitting layer 5 is formed is transferred into a vacuum vapor deposition apparatus, and after the apparatus is roughly evacuated by an oil rotary pump, the degree of vacuum in the apparatus becomes 2.4 × 10 ⁻⁴ Pa or less. After exhausting using a cryopump, a compound (BAlq) represented by the following structural formula C1 was laminated by a vacuum deposition method to obtain a hole blocking layer 6. The deposition rate was controlled in the range of 0.8 to 1.2 liters / second, and the hole blocking layer 6 having a film thickness of 10 nm was formed by being laminated on the light emitting layer 5. The degree of vacuum at the time of vapor deposition was 2.4 to 2.7 × 10 ⁻⁴ Pa.

Subsequently, tris (8-hydroxyquinoline) aluminum (Alq3) represented by the following structural formula C2 was heated and evaporated to form an electron transport layer 7. The degree of vacuum during deposition is 0.4 to 1.6 × 10 ⁻⁴ Pa, the deposition rate is controlled in the range of 1.0 to 1.5 Å / sec, and a film with a thickness of 30 nm is formed on the hole blocking layer 6. To form an electron transport layer 7.

Here, the element that has been deposited up to the electron transport layer 7 is once taken out from the vacuum deposition apparatus into the atmosphere, and a 2 mm wide striped shadow mask is used as a cathode deposition mask. The device was placed in close contact with each other so as to be orthogonal to each other, placed in another vacuum deposition apparatus, and evacuated until the degree of vacuum in the apparatus was 6.4 × 10 ⁻⁴ Pa or less in the same manner as the organic layer.

First, lithium fluoride (LiF) was controlled as the electron injection layer 8 at a deposition rate of 0.1 to 0.4 liter / second and a degree of vacuum of 3.2 to 6.7 × 10 ⁻⁴ Pa using a molybdenum boat. A film having a thickness of 0.5 nm was formed on the electron transport layer 7. Next, aluminum is similarly heated by a molybdenum boat as the cathode 9 and controlled at a deposition rate of 0.7 to 5.3 liters / second and a degree of vacuum of 2.8 to 11.1 × 10 ⁻⁴ Pa to a film thickness of 80 nm. An aluminum layer was formed. 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, about 1 m on the outer periphery of a 23 mm x 23 mm size glass plate
A photo-curing resin (ThreeBond 3Bond 3124) was applied with a width of m, and a moisture getter sheet (Dynic Co., Ltd.) was installed in the center. 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. With respect to the obtained device, a change in luminance was measured when a constant direct current was continuously applied in an environment maintained at 23 to 25 ° C. The current value was set to a value at which the luminance immediately after energization was 2500 cd / m ² . The results are shown in Table 1.
(Comparative Example 1)
In Example 1, the organic electroluminescent element shown in FIG. 1 was produced in the same manner as in Example 1 except that the hole transport layer 4 was formed as follows.

  A hole transporting layer-forming coating solution containing a hole transporting compound (H2) having no crosslinking group (H2) (weight average molecular weight 9240, number average molecular weight 4700) and toluene as a solvent was prepared, and spin coating was performed under the following conditions. A film was formed by a coating method and dried by heating to form a hole transport layer 4 having a thickness of 20 nm.

<Hole transport layer coating solution>
Solvent Toluene
Coating solution concentration H2: 0.4% by weight
<Film formation conditions>
Spinner speed 1500rpm
Spinner rotation time 30 seconds
Spin coat atmosphere In nitrogen
Heating conditions In nitrogen, 170 ° C, 30 minutes
As described above, an organic electroluminescent element having a light emitting area portion having a size of 2 mm × 2 mm was obtained. The luminance change of the obtained element was measured in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 2)
In Example 1, the organic electroluminescent element shown in FIG. 1 was produced in the same manner as in Example 1 except that the hole transport layer 4 was formed as follows.
The substrate on which the hole injection layer 3 is formed is transferred into a vacuum vapor deposition apparatus, and after roughly evacuating the apparatus with an oil rotary pump, the cryogenic pressure in the apparatus is reduced to 2.0 × 10 ⁻⁴ Pa or less. After exhausting using a pump, the compound (H3) which does not have a crosslinking group was laminated | stacked by the vacuum evaporation method, and the positive hole transport layer 4 was obtained. The deposition rate was controlled in the range of 0.8 to 1.2 liters / second, and the hole transport layer 4 having a film thickness of 16 nm was formed by being laminated on the hole injection layer 3. The degree of vacuum during the deposition was 2.2 to 2.5 × 10 ⁻⁴ Pa.

Thereafter, the sample on which the hole transport layer 4 was formed was taken out from the vacuum deposition apparatus, and the layers after the light emitting layer 5 were formed in the same manner as in Example 1.
As described above, an organic electroluminescent element having a light emitting area portion having a size of 2 mm × 2 mm was obtained. The luminance change of the obtained element was measured in the same manner as in Example 1. The results are shown in Table 1.

As is clear from Table 1, the organic electroluminescent device of Example 1 having a hole transport layer containing a crosslinkable compound was used in Comparative Examples 1 and 2 in which a compound having no crosslinkable group was used for the hole transport layer. It is clear that a more stable element can be obtained with a lower luminance drop during driving as compared with the above element.
(Example 2)
In the same manner as in Example 1, an anode and a hole injection layer were formed on the substrate.

Subsequently, the hole transport layer 4 was formed on the hole injection layer by the wet deposition method according to the following procedure. As a crosslinkable hole transport compound, a coating solution containing a compound represented by the following structural formula (H4) and toluene as a solvent was prepared, and a film was formed by spin coating under the following conditions. Thereafter, a 500 W ultra-high pressure mercury lamp light was irradiated using the exposure apparatus UX-1000SM-ACS01 manufactured by USHIO ELECTRIC CO., LTD. The light irradiation was performed in an atmosphere having an air temperature of 23 ° C. and a relative humidity of 60% with an integrated irradiation light amount of 5 J / cm ² and an irradiation time of 179 seconds. The intensity of 365 nm light (g line) on the irradiated surface was 28 mW / cm ² . Furthermore, after light irradiation, heating was performed at 230 ° C. for 1 hour in a nitrogen atmosphere using a hot plate.

<Hole transport layer coating solution>
Solvent xylene
Coating concentration H4: 1% by weight
<Film formation conditions>
Spinner speed 1500rpm
Spinner rotation time 30 seconds
Spin coat atmosphere In air
Thus, a uniform hole transport layer 4 having a thickness of 20 nm was obtained.

Next, in forming the light emitting layer 5, a coating solution for forming a light emitting layer containing the organic compounds (E1) and (E2), an iridium complex (D1) as a low molecular light emitting material, and xylene as a solvent is prepared, A film was formed on the hole transport layer 4 by a spin coat method under the conditions shown below, followed by heating and drying to obtain the light emitting layer 5 with a film thickness of 80 nm.
<Light emitting layer coating solution>
Solvent xylene
Coating solution concentration E1: 1.0% by weight
E2: 1.0% by weight
D1: 0.1% by weight
<Film formation conditions>
Spinner speed 1500rpm
Spinner rotation time 60 seconds
Spin coat atmosphere In nitrogen
Heat drying conditions 0.01 MPa, 130 ° C., 1 hour
Here, the substrate on which the light emitting layer 5 is formed is transferred into a vacuum deposition apparatus, and after the apparatus is roughly evacuated by an oil rotary pump, the degree of vacuum in the apparatus becomes 2.7 × 10 ⁻⁴ Pa or less. After exhausting using a cryopump, a compound represented by the following structural formula C3 was laminated by a vacuum deposition method to obtain a hole blocking layer 6. The deposition rate was controlled in the range of 0.8 to 1.2 liters / second, and the hole blocking layer 6 having a film thickness of 5 nm was formed by being laminated on the light emitting layer 5. The degree of vacuum at the time of vapor deposition was 1.7 × 10 ⁻⁴ Pa.

Thereafter, in the same manner as in Example 1, an electron transport layer, an electron injection layer, and a cathode were formed, and sealing treatment was performed to obtain an organic electroluminescent element having a light emitting area portion having a size of 2 mm × 2 mm. Table 2 shows the time when the luminance of the obtained element was reduced to 800 cd / m ² and the voltage at that time.
(Comparative Example 3)
An organic electroluminescent element was obtained in the same manner as in Example 2 except that the hole transport layer was not provided. Table 2 shows the time when the luminance of the obtained element was reduced to 800 cd / m ² and the voltage at that time.
It has been found that by having a hole transport layer formed by crosslinking a crosslinkable compound, a device having a long lifetime by low voltage driving can be obtained.

(Example 3)
In the same manner as in Example 1, an anode and a hole injection layer were formed on the substrate.
Subsequently, a hole transport layer 4 was formed on the hole injection layer 3 by a wet film formation method according to the following procedure. A coating liquid containing a compound represented by the following structural formula (H5) as a crosslinkable hole transport compound and toluene as a solvent was prepared, and a film was formed by a spin coating method under the following conditions. Thereafter, irradiation with 500 W ultra-high pressure mercury lamp light was performed using an exposure apparatus UX-1000SM-ACS01 manufactured by USHIO INC. The light irradiation was performed in an atmosphere with an air temperature of 23 ° C. and a relative humidity of 60% with an integrated irradiation light amount of 5 J / cm ² and an irradiation time of 179 seconds. The intensity of 365 nm light (g line) on the irradiated surface was 28 mW / cm ² . Furthermore, after light irradiation, heating was performed at 230 ° C. for 1 hour in a nitrogen atmosphere using a hot plate.

<Hole transport layer coating solution>
Solvent Xylene Coating solution concentration H5: 1.0% by weight
<Film formation conditions for hole transport layer 4>
Spinner speed 1500rpm
Spinner rotation time 30 seconds Spin coat atmosphere In the air Next, in forming the light emitting layer 5, the organic compound (E1), (E2), light emission containing iridium complex (D1) as a low molecular light emitting material and xylene as a solvent. A layer-forming coating solution was prepared, formed on the hole transport layer 4 by a spin coat method under the conditions shown below, and dried by heating to obtain a light-emitting layer 5 having a thickness of 50 nm.

<Light emitting layer forming coating solution>
Solvent Xylene Coating solution concentration E1: 1.0% by weight
E2: 1.0% by weight
D1: 0.1% by weight
<Film formation conditions of the light emitting layer 5>
Spinner speed 1500rpm
Spinner rotation time 30 seconds Spin coating atmosphere In nitrogen Heating condition Under reduced pressure (0.1 MPa), 130 ° C., 1 hour Here, the substrate on which the light emitting layer 5 has been deposited is transferred into a vacuum deposition apparatus, and the vacuum inside the apparatus After evacuating until the degree becomes 2.7 × 10 ⁻⁴ Pa or less, an organic compound (C
3) was laminated | stacked by the vacuum evaporation method, and the hole-blocking layer 6 was obtained. The deposition rate was controlled in the range of 0.8 to 1.2 liters / second, and the hole blocking layer 6 having a film thickness of 5 nm was formed by being laminated on the light emitting layer 5. The degree of vacuum at the time of deposition was 1.7 × 10 ⁻⁴ Pa.

The electron transport layer 7 and subsequent layers were formed in the same manner as in Example 1 to produce an organic electroluminescent element. Table 3 shows the drive life and drive voltage of the obtained element.
(Comparative Example 4)
An organic electroluminescent element was produced in the same manner as in Example 3 except that the hole transport layer 4 was not provided. Table 3 shows the drive life and drive voltage of the obtained element.

(Example 4)
An organic electroluminescent element was produced in the same manner as in Example 3 except that the hole transport layer 4 was formed as follows. Table 3 shows the drive life and drive voltage of the obtained element.
The hole transport layer 4 was formed by a wet film formation method according to the following procedure. As a crosslinkable hole transport compound, a coating liquid containing a compound represented by the following structural formula (H6) (weight average molecular weight: 36000, number average molecular weight: 21000) and toluene as a solvent is prepared, and spin coating is performed under the following conditions. A hole transport layer 4 having a thickness of 20 nm was formed by forming a film and crosslinking by heating.

<Hole transport layer coating solution>
Solvent Toluene Coating solution concentration H6: 0.4% by weight
<Film formation conditions for hole transport layer 4>
Spinner speed 1500rpm
Spinner rotation time 30 seconds Spin coating atmosphere In nitrogen Heating condition In nitrogen, 230 ° C., 1 hour (Example 5)
The same procedure as in Example 4 was conducted except that the crosslinkable hole transport compound (H6) was replaced with a crosslinkable hole transport compound (H7) (weight average molecular weight: 41000, number average molecular weight: 22000) shown in the following structure. Thus, an organic electroluminescent element was produced. Table 3 shows the drive life and drive voltage of the obtained element.

(Example 6)
The same procedure as in Example 4 was conducted except that the crosslinkable hole transport compound (H6) was replaced with a crosslinkable hole transport compound (H8) (weight average molecular weight: 92000, number average molecular weight: 24000) shown in the following structure. Thus, an organic electroluminescent element was produced. Table 3 shows the drive life and drive voltage of the obtained element.

(Example 7)
The same procedure as in Example 4 was conducted except that the crosslinkable hole transport compound (H6) was replaced with a crosslinkable hole transport compound (H9) (weight average molecular weight: 41000, number average molecular weight: 25000) shown in the following structure. Thus, an organic electroluminescent element was produced. Table 3 shows the drive life and drive voltage of the obtained element.

(Example 8)
The same procedure as in Example 4 was conducted except that the crosslinkable hole transport compound (H6) was replaced with a crosslinkable hole transport compound (H10) (weight average molecular weight: 60000, number average molecular weight: 20000) shown in the following structure. Thus, an organic electroluminescent element was produced. Table 3 shows the drive life and drive voltage of the obtained element.

Table 3 shows the drive life and drive voltage of the organic electroluminescent elements produced in Examples 3 to 8 and Comparative Example 4. In the table, the drive life is the time until the brightness is reduced to 60% of the initial brightness, the initial brightness is the initial brightness when the drive life is measured, and the voltage is the voltage at the start of the drive test.
As is apparent from Table 3, the organic electroluminescent element of the present invention has a long lifetime.

Example 9
An organic electroluminescent element was produced in the same manner as in Example 1 except that the light emitting layer was formed as follows.
In forming the light emitting layer 5, the organic compounds (E1) and (E2), the iridium complex (D1) as the low molecular weight light emitting material, the iridium complex (D2) shown below, and the light emitting layer forming coating containing toluene as the solvent. A solution was prepared, and a film was formed on the hole transport layer 4 by a spin coating method under the conditions shown below, followed by drying by heating to obtain a light emitting layer 5 with a film thickness of 60 nm.

  Table 4 shows the drive life and drive voltage of the obtained element.

<Light emitting layer coating solution>
Solvent Xylene Coating solution concentration E1: 1.0% by weight
E2: 1.0% by weight
D1: 0.1% by weight
D2: 0.1% by weight
<Film formation conditions of the light emitting layer 5>
Spinner speed 1500rpm
Spinner rotation time 30 seconds Spin coat atmosphere Nitrogen Heating conditions Under reduced pressure (0.1 MPa), 130 ° C., 1 hour (Comparative Example 5)
An organic electroluminescent element was produced in the same manner as in Example 9 except that the hole transport layer 4 was formed in the same manner as in Comparative Example 1. Table 4 shows the drive life and drive voltage of the obtained element.

Table 4 shows the drive life and drive voltage of the organic electroluminescent elements produced in Example 9 and Comparative Example 5. In the table, the drive life is the time until the brightness is reduced to 60% of the initial brightness, the initial brightness is the initial brightness when the drive life is measured, and the voltage is the voltage at the start of the drive test.
As can be seen from Table 3, the organic electroluminescent device of the present invention has an improved driving voltage and a long life.

(Example 10)
An organic electroluminescent element was produced in the same manner as in Example 1 except that the hole transport layer and the light emitting layer were formed as follows.
A coating liquid for forming a hole transport layer containing a crosslinkable hole transport compound (H11) (weight average molecular weight: 60000, number average molecular weight: 22000) represented by the following structural formula was prepared, and spin coating was performed under the following conditions. A hole transport layer 4 having a thickness of 20 nm was formed by film formation by the method and crosslinking by heating.

<Hole transport layer coating solution>
Solvent Toluene Coating solution concentration H11: 0.4% by weight
<Film formation conditions for hole transport layer 4>
Spinner speed 1500rpm
Spinner rotation time 30 seconds Spin coat atmosphere Heating condition in nitrogen Heating condition in nitrogen, 230 ° C., 1 hour Next, in forming the light emitting layer 5, the organic compound (E3) shown below and an organic compound (D3) as a low molecular light emitting material And a light emitting layer-forming coating solution containing toluene, prepared by spin coating on the hole transport layer 4 under the conditions shown below, and dried by heating to give a light emitting layer 5 having a thickness of 40 nm. Got.

<Light emitting layer coating solution>
Solvent Toluene Coating solution concentration E3: 0.80 wt%
D3: 0.08% by weight
<Film formation conditions of the light emitting layer 5>
Spinner speed 1500rpm
Spinner rotation time 30 seconds Spin coating atmosphere In nitrogen Heating conditions Under reduced pressure (0.1 MPa), 130 ° C., 1 hour The driving life and driving voltage of the obtained element are shown in Table 5. In the table, the drive life is the time until the brightness is reduced to 60% of the initial brightness, the initial brightness is the initial brightness when the drive life is measured, and the voltage is the voltage at the start of the drive test. Moreover, dope concentration represents weight% of the electron-accepting compound (A1) with respect to a polymeric hole transport material.

(Example 11)
An organic electroluminescent element was produced in the same manner as in Example 10 except that the hole injection layer 3 was formed as follows. Table 5 shows the drive life and drive voltage of the obtained element.
Polymer hole transport material (crosslinkable hole transport compound) having a repeating structure represented by the following structural formula (P2) (weight average molecular weight: 66000, number average molecular weight: 31000), electron accepting compound (A1) and solvent A coating solution for forming a hole injection layer containing ethyl benzoate was prepared. A film of this coating solution was formed on the anode 2 by the spin coat method under the following conditions, followed by heat crosslinking to obtain a hole injection layer 3 having a thickness of 30 nm.

<Hole injection layer coating solution>
Solvent Ethyl benzoate Coating solution concentration P2: 2.0% by weight
A1: 0.2% by weight
<Film formation conditions for hole injection layer 3>
Spinner speed 1500rpm
Spinner rotation time 30 seconds Spin coat atmosphere In air Heating conditions In air, 230 ° C., 1 hour (Example 12)
The hole injection layer 3 was formed by replacing the polymer hole transport material (P2) with the polymer hole transport material (P3) (weight average molecular weight: 28000, number average molecular weight: 16000) represented by the structure shown below. Otherwise, an organic electroluminescent device was produced in the same manner as in Example 11. Table 5 shows the drive life and drive voltage of the obtained element.

(Example 13)
The hole injection layer 3 is formed by changing the polymer hole transport material (P2) to the polymer hole transport material (P4) (weight average molecular weight: 52000, number average molecular weight: 33000) represented by the structure shown below. Otherwise, an organic electroluminescent element was produced in the same manner as in Example 11. Table 5 shows the drive life and drive voltage of the obtained element.

1. substrate
2. anode
3. Hole injection layer
4). Hole transport layer
5. Luminescent layer
6). Hole blocking layer
7). Electron transport layer
8). Electron injection layer
9. cathode

Claims (5)

In the organic electroluminescence device having an anode, a cathode, and a hole injection layer, a hole transport layer, and a light emitting layer in this order between the anode and the cathode,
The hole injection layer is a layer formed by dissolving or dispersing a hole transport material containing an aromatic tertiary amino group as a structural unit in a main skeleton in a hydrophobic solvent and performing wet film formation,
The hole transport layer is a layer der formed by crosslinking a crosslinking compound is, after deposition, a layer obtained by electromagnetic energy radiation such as heating and / or light, the crosslinkable compounds, crosslinked look containing a repeating unit having a group is a polymer containing a repeating unit represented by formula (II),

(In the formula, Ara and Arb each independently represent an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent.)
The light emitting layer is a layer formed by wet film formation of a low molecular light emitting material,
Organic electroluminescent device. 2. The organic electroluminescent device according to claim 1, wherein the light emitting layer includes the low molecular light emitting material as a dopant material, and further includes a low molecular charge transport material as a host material. The organic electroluminescent element according to claim 1, wherein the hole injection layer contains the polymer hole transport material and an electron accepting compound. The organic electroluminescent display which has the organic electroluminescent element as described in any one of Claims 1-3. Organic EL illumination which has the organic electroluminescent element as described in any one of Claims 1-3.

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